Where do you think the members of the fellowship were during "The Hobbit"?

[dancing spawn of ungoliant]

he could have easily become friends with Aragorn in that time.

Yep, there's plenty of time but I had understood that Aragorn didn't spent much time in Rivendell ...
(from Appendix B in LotR, these are not straight quotes due to the lack of english edition)
2942:Bilbo returns to the Shire with the Ring.
2951:Aragorn meets Arwen in Rivendell and leaves to the wild.
3001:Bilbo's birthday party.Gandalf gets some information about Gollum and asks Aragorn for help.
3002:Bilbo goes to Rivendell.
3009:Gandalf and Aragorn hunts Gollum every now and then for the next 8 years.
3017:Aragorn finds Gollum.

well, I don't know what Aragorn exactly did from the year 3001 to 3008 but I assume that he didn't just stay at home. But yes, they might have become friends then.