It is a head to head league, so the guy with Ellsbury is not technically out of it. His team sucks though, and the other guy is in first place. It's very suspicious, but I also get the feeling this guy is not the brightest. This is the same guy that took Pedroia with the #1 overall pick in the draft. I am going to let it go for now.
there are quite a few teams that grabbed Hanley, Crawford or Longoria in the top 5 who would LOVE to have been stupid enough to take Pedroia instead.
The trade is certainly suspicious, but there are a couple other details that are necessary to judge it.
keeper league? if so, what are the keeper rules and penalties? I.e., if Roberts can be kept for a last round pick and Ellsbury requires a 2nd or 3rd rounder (i don't remember where he was drafted this year) - or some comparable difference in auction values - there's a good case to be made for Roberts.
is the other team working with a giant hole at 2B or 3B?
If the team giving up Ellsbury is just plugging Roberts into the OF spot, there's legitimate reason to question this.