I still would like him on the Cubs but I think that his SB, which are a large part of his appeal, will be taking a hit. 1) you have Yadier as I pointed out. It may seem absurd but the guy is a stud in a big part of baserunning and the Cubs play the Cards a bunch. 2) you have Soriano batting in the 2 hole. While he has the pop to knock Roberts in if he steals, he likes to swing and will likely do so. 3) I think that while Sweet Lou talked some about playing more aggressively, I did not see a lot of it. I saw baserunners and hitters working together to try to distract pitchers but I think that he's as much a hit & run from a strategy perspective as a straight stealer.
I think Roberts to the Cubs will be great for the Cubs but will push Roberts to the 20-30 range for SB. Maybe even less.