"What good is Vic Beasley if he's only going to play linebacker?" some of you cried, your voices shaking with rage. You'll be glad to know you can settle down, friends.
As anticipated, Beasley has dual roles on defense. On early downs and in obvious run situations, he'll be at strong side linebacker, where he'll rush the passer and occasionally drop into coverage as needed. In those situations, the Falcons will put more bulk up front, including Ra'Shede Hageman at one of the defensive end spots.
In nickel situations and on third downs, though, Beasley should be at defensive end much of the time, rushing the passer as part of a more nimble defensive line. As long as he's chiefly asked to use his ability to get after the quarterback, he should fare well in either role, and you should not be freaked out that he's going to be asked to spend some time at linebacker. The Falcons know what he does well and will ask him to do it regardless of where he lines up, and that's really all we can ask for.
This is also a big part of Dan Quinn's defensive strategy, which involves heavy rotation of players to keep them fresh and moving players around according to the situation. The good news is that Beasley will be one of the defense's few full-time players, so he'll have a ton of opportunities to improve on the four sacks he amassed in his rookie season. I fully expect he'll do so.