Since WWE acquired Dean Ambrose, they have had him do some incredible stuff down in FCW. While it's said that they may not be too impressed with his physique (because WWE, i.e. Vince McMahon and HHH like bodybuilders) they are VERY impressed with his mic skills and in-ring work and see him as a future top heel for the company.
For Seth Rollins, WWE saw fit to make him the first ever NXT Champion, and seem to have a lot of faith in him. They see him as a future CM Punk. But, unfortunately, it's, again, been said that they aren't too impressed with his mic skills, but are high on his in-ring work and athletic ability.
In regards to Roman Reigns, WWE have said that this guy has the look of a future star. While he could learn a thing or two from Dean Ambrose's mic skills, they are EXTREMELY high on him. They feel he's a guy who could go toe-to-toe with the likes of his cousin The Rock, or John Cena in a main event situation.
In my personal opinion, Roman Reigns is the future "Face" of the WWE.
When WWE debuted "The Shield", a lot of WRESTLING FANS were excited that Rollins and Ambrose (two past indy stars, with a history together - much like Danile Bryan and CM Punk - had aligned together on TV) joined to up to help fellow former indy sensation CM Punk on WWE TV against Ryback. But many were confused as to why Roman Reigns - a man straight out of WWE's developmental system with no indy scene past - was helping these two men.
Many believe it should have been Kassius Ohno (former ROH/indy star Chris Hero) that debuted in The Shield.
But if you are going to debut a dominant force, you're better off having a powerhouse in the group, and Reigns is just that.
I think there is reason for it. I also feel there is a reason why everytime they come to the ring through the crowd, that Rollins and Ambrose are walking seperate from Reigns.
Reigns will eventually be booted from The Shield and turn face; thus kick starting his career to the top of WWE. Maybe Kassius Ohno will join The Shield then. Maybe not.
Then again - only an assumption. Time will tell...