In his dreams, he remembers. Before the thoughts, memories, worries, when he was a different creature. Glimpses so brief, it took him years to realize what they were. He was jaded, left wanting by these fantasies of a simpler life. After he escaped, he didn't trust anyone, didn't want to get to know anyone. As far as he was concerned, they'd all failed him, any one of them could've saved him from the lab, but they hadn't, and he hated them for it.
Then along came Groot. He caught one look at the raccoon and suddenly he was following him everywhere. Acted like he knew him from somewhere. Rocket was unsettled by how instantly he understood Groot's speech. He could feel it, he understood because of what he used to be; it gave him an animal connection to nature and attentiveness to body language. And now that he thought about it, Groot looked awfully familiar too. The more they talked, the clearer his dreams became. Eventually he started seeing flashes of Groot's face, always from above, like he was nestled in the top of Groot's head where he'd so often longed to sit.
He knew it sounded silly but; were they destined to meet again?
He remembered back in those days, he was very affectionate towards Groot. He was his protection, shelter, and friend, and part of Rocket wondered if he'd kept him around so long subconsciously, in hopes of rebuilding that bond. Or, he thought more privately, maybe they were meant to reunite when he was like this, so their relationship could be something more.
He thought of it often. They'd already formed such a close relationship before, Groot was the link to his past. He'd never be so close to anyone else.
He loved him, of course he did. Groot was everything he remembered, everything he could remember. He was all he knew.
Some of it was nostalgic, clinging to every last shred of memory he had of a happier life, and Groot was the happiest part of that life. He needed him now, more than he had before. He made him feel secure, important, equal, loved. He helped him navigate a world with new eyes.