
hmmm I don't recall him being a "rat" as in any specific organization. He was a street rat, in the meaning that he would try to scrounge up any food he could. She was part of a group of kids that had been together for a little while at least, I don't know how close you need them to be for them to be "close", but *spolier*
he will remember her and be concerned about her and try to get to Border Town to find her, so that means something.

No, the poor guy was a rat. He would try to take care of the other kids but they're still under this guy who's a dick, and wouldn't mind killing them if they disobeyed him. They'll be saved later when Roland is determined to get rid of the rat organisations in that town, and that's when he decides to improve his life and search for the witch.

he was trying but he wasn't really a rat, not a member just a.. collaborator? He worked for that guy when trying to survive,but he was taking advantage of him and not letting him in. That's why Roland saved him when he got rid of the rats, he got rid of all of them regardless of redeeming qualities - they had none. He was always a good kid, only trying to survive, but he always thought about Paper and wanted to catch up with her.
Why the boy couldn't go with her?