Nominally naming Richie Incognito as the Rams starting center and moving Setterstrom to right guard gives the Rams a beefy middle to go with their offseason acquisition of Jacob Bell at left guard.
First, look at size here. Romberg, now #2 on the depth chart at C, is 6' 2" 298 lbs, the smallest of the trio with Setterstrom listed at 6' 4" 314 lbs and Cogs listed at 6' 3" 330 lbs. Now, look beyond size. Setterstrom's still somewhat unproven, but he's got good agility and athleticism to go mobile without losing anything; he can pull when the play calls for a pulling guard and he can use that field vision to keep out defensive linemen looking to crash the pocket. Since being drafted in 2006, he's added more than 30 lbs to his frame, and has improved in one-on-one blocking situations. Obviously, the coaches have seen some improvement from him in minicamp and OTAs to be making this declaration ahead of training camp.
Since Richie Incognito learned to channel his nasty disposition onto the playing field, he's emerged as one of the team's best blockers, in my opinion. He;s played C, G and OT, but he's been at his best in the interior. With DTs getting bigger and faster in the NFL, putting Cogs at center makes sense as his skills can keep defenders out in pass protection and push them aside on the run. Now, on the snap, Cogs looked a little raw at times when he filled in for Andy McCollum in 2006, but that's something he should be able to improve on with practice. There's no doubting the results though from 2006 when the Rams had Cogs and Setterstrom on the interior at various points throughout the season; they ranked second in the league in adjusted line yards (4.77) in the middle of the field.
This could all change come camp time later this summer.