I agree that Roddy is the WR to target if you're going to make a deal.
I'd probably rather move Floyd than Jennings given that Floyd is battling a hammy injury and long-term may have VJax to steal targets.
But more generally, why are you trying to upgrade your WRs? Nicks + Megatron is a pretty solid 1-2 WR pairing unless you're in a six-team league or something, and being able to play the matchups between Floyd/Jennings at WR3 means you're pretty stacked both talent and depth-wise there. I don't know how the rest of your roster looks, but I might try to snag some RB depth or a top DST or a solid QB or something if you're really intent on dealing Keller. Otherwise, stand pat.