As you might imagine from Roth's size, he is very good at setting the edge and playing the run. Since he came to Cleveland, he has developed into a pretty good power pass rusher. He only had 3.5 sacks in 2010 but he also had 10 hits and 40 pressures according to Pro Football Focus. According to Focus, 13.66% of Roth's pass rushing attempts after joining the Browns resulted in either a sack, hit, or pressure. For perspective, Clay Matthews rates at 12.78% since 2009. (Matthews has a lot more rushing attempts and has put up bigger numbers. Don't think I'm saying Roth is better.)
Roth's weakness as one might imagine from his size is he is not terribly nimble dropping into coverage. He is similar to Calvin Pace in some of his strengths and weaknesses, although Roth was much more productive in 2010.
He might very well get the blessing of Rob Ryan for whom he played. This would not generate huge headlines because of the low sack numbers, but Roth could serve as a huge upgrade.