Here's what Mocking The Draft said:
Whenever free agency comes around, linemen Justin Blalock, Tyson Clabo and Harvey Dahl are all free agents for the Falcons. They may choose not to bring all of them back. If they don't, a lineman with versatility is needed. That is what Gilbert provides them. He was a college tackle for Florida who projects as a guard because he's not incredibly fluid or athletic.
Can't blame them for looking to solidify the offensive line. The largest reason the Falcons are a good team is because QB Matt Ryan is healthy and has time to throw. Might as well make one of your strengths even stronger. I like this pick.
For the full explanation of the pick, check out Mocking The Draft.