Guess who finally kicked her ass to finish things? Ayee, das me
So here is Rosa's timeline along with the history of hers, since it'll be too long to add it to her profine which you can see here - fav.me/d8h20kb
I guess it's really understandable which figure is which period of her life. I don't intend to invent a bicycle but I hope you'll like it.

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Childhood

0-5
Rosalinda was born on an island of Yanchen in North Blue in a village in the woods. The population of the island was rather scattered but their community was large compared to smaller ones. She was born into a family of music instrument's maker. Her mother and father studied the science of making beautiful masterpieces carved out of wood and earned a living out of it. 
They lived in a small cozy cottage with her parents and grand parents. Rosa was a quiet, kind and delicate child, brought up in safety and nature. She loved having walks in the nearby woods, even though it was dangerous sometimes. With her parents being quite busy sometimes, she loved to spend time with her grandmother and grandfather. Her grandma brought her love to singing and doing chores, her granddad was great flutist, teaching her the basics of the instrument. Even as a child Rosa was shy and easily offended, thus didn't have a lot of her peers as friends. She also possessed a prominent haki ability she wasn't mature enough to master, so she tried to isolate herself from people, until she felt better with it.
5-12
When she was 5, her granddad died because of his age and her grandmother followed him in a year. That was the first time she was facing a death of her loved ones, but with her parents support she dealt with her grief in some time. To help her, the family moved to a different larger settlement, closer to the seaside. This not only gave her parent's business a lift, it also opened wider perspectives for her. She started attending school and a music school as well, made new friends and became more outgoing and cheerful than before. Life in a town refreshed her and made her generally to a more lively and lovely child than she already was. With her growing interest to things, she discovered her wish to see the world around her and persuaded her parents to arrange a vacation trip for them to visit nearby islands.
After her twelve birthday, they set sail on their trip aboard a big trade ship. Unfortunately, that ship transferred the infamous Ina-Ina no mi under cover to the Marineford. Hidden in their storage, they kept it a secret among the other plenteous cargo. 
Rosa, led by her haki and curiosity happened to play in the cargo hold and find it without a knowledge of the nature of her windfall, when the ship was attacked by pirates, who had the information, that the fruit is on board. They dragged the whole crew and passengers on the deck, intimidating them, what they'll kill everyone, if they don't handle the fruit to them. Rosalinda, out of fear, gave it to them, hoping to save everyone. But if was already bitten at. It made the pirates furious, but they couldn't risk killing her and waiting for the fruit to appear elsewhere. She's young and scared enough to be made into a tool, so they took her as a hostage, killing everyone else and sinking the ship.

Teen years

13-14
The crew, who were claiming themselves to be pirates, turned out to be majorly engaged into slave trade under the banner of one of the Four Emperors of the Sea - Kaido. They were a smaller group, hoping to promote through the devil fruit users, who could assist them in their deeds. And they had plans to make Rosalinda one of them. Her first year was humilating and terrible, they used fear and pain to control her, so she could never turn her ability against them. She also had to learn how to deal with it - it was hard, since she had to wear kairoseki handcuffs half of the time. She was poorly fed and just kept alive until she was needed - mostly for hunting on DF users or being forced to harm people. She never enjoyed that and tried to opposed, but her tries to help people were futile. She soon started to despise herself for being helpless, for keeping a miserable existence, for suffering all that pain for nothing. The anxiety she felt made her try to hurt herself several times in order to commit suicide. She never achieved that goal and was saved by the very people she hated.
15-19
After that her conditions changed a little, there was always someone to look if she's feeding properly and doesn't try to herself anymore. Their crew sailed from one human sale auction to another, and Rosa's loathing of herself went to another stage - in her abilities affecting her. She wished for herself to perish for so so long, that the rejecting effect she never should have been experiencing, progressed quickly. Since there was no help and no cure for that, they just used painkillers and different sorts of drugs to keep her standing. Suffering through physical pain eased her moral struggles a little bit - she took it as punishment of assisting the slave traders. Time made her very indifferent to things - she didn't have moral strength to fight back or help others anymore, she isolated herself from being alike her abusers.
In time they got more involved into the business, and grew quite famous. So also did she, becoming an infamous 'Mind Slasher'. They still used her to fight against devil fruit users and her ability to strip them out of their abilities, so the rest of the crew could cuff them with kairoseki.
They arranged a human auction house disguised as a Colosseum for pirates. The losers eventually were turned into slaves.That was the place where Rosa first met Law.
He came to the Colosseum out of interest and wanting to acquire the Ina-Ina no mi user. He intentionally went to have a fight with her and got caught. However, everything went according to plan, and he saw that the conditions Rosa was put in, tried to pick a conversation with her. She was a hard nut to crack, since she already lost all her hope, but being quite manipulative and surprisingly understanding towards her, he caught her eye. She thought that maybe helping him to escape slavery could be her last chance for a long desired redemption - she knew she won't live long anyway. Using her haki to understand his intentions, she was shocked at amounts of pain and anger somebody else was going through.
After unplanned and quite rushed escape attempt, a huge fight escalated between Rosa's masters and Heart pirates, coming to aid their captain. During the fight side by side with Law and finally being courageous enough to stand against those who abused her for so long, she snapped out, letting all her resentment, hate and anger out in order to help people, who were kind to her once in a long while. But as soon as the effect of her drugs stopped to last, her condition became critical and on the edge of death, Law made the decision to take her to the sub. Maybe he felt pity for her existence or maybe still needed her abilities no matter what.

Early Adulthood

20-22
Rosa was taken into the crew after Law successfully kept her alive. She had nowhere to go back to, and she basically owed her life to him. He insisted, that she made her mind on her own, not directly forcing her to accept. Understanding there was no real choice for her to make, she agreed and here the period of her adaptation started. She suffered through very strong PTDS and was unsociable to the extreme. It took her time, care and Law as a doctor (cause the crew was scared of her for some time and she didn't talk to anyone else) to calmly and thoroughly help her accept and overcome the past she's been through. After a year of treatment she slowly started showing off her real character and get along with the crew. She started to see the world in it's diversity and read a lot to be of help. Discovering a fast learner talent, she kept up with the crew and studied to give the first aid treatment in battles and assistance during operations. At that time Rosa used to wear a fluffy hat under the hood of her boiler suit, which covered her face almost completely. (and that's why she didn't get a bounty cause her face was practically almost covered) She was adored because of her immense dedication to the crew and captain especially and shy but quite engaging and kind personality.
After another half a year passed, after an accident Law discovered what she was incurable ill. She hid it long enough already out of resignation and to keep everyone from worrying about her and thinking as of a burden. After asking her if she knew about her illness, Law was quite shocked to know, what she knew what she was dying all along and accepted that some time ago, allowing herself to see the world a little before she perishes. 
Reminded of his own past and refusing to lose a crew member he gained with some amounts of effort, the captain protested against her futile attempts to calm him down. He assured Rosa, what as her captain and doctor he'll find the cure to her illness and she won't be dying on his watch. Even though she doubted that fact, she still received painkillers, vitamins and what not to keep her safe and sound. The crew was also instructed how to react if she even gets an attack, though only Law knows the real danger and nature of her illness, since she asked him to keep this between them. Because of that he forbids her to overuse her abilities or leave the sub for too long. 
23-24
During the timeskip she finally got rid of the fluffy hat and got her earmuffs - that was a gift for the crew for her birthday. They actually discovered her ability to play mandolin and flute and sing, so she became an official position as a musician in the crew. Her condition was and is generally stable more or less at the moment. She feels really comfortable and happy with the crew and taking care of them is her favorite activity. She became not only more committed but also more serious, leading a pirate's life. She kept herself engaged into serious fights, using her DF abilities for protection, even if she had to suffer the consequences. She genuinely believes in her captain decisions, even if they meant for the crew to be separated, when Law left for Punk Hazard.


And that's it folks since that's just BRIEF history.
And Rosa belongs to me
One Piece and all characters mentioned belong to