Sheamus - Heel
Orton - Heel (the crowd will be sick of him again in 6 months time)
Big Ay and The New Day - Heels
Cesaro - Face
Reigns - Heel
Cena - Heel (he could be one of the all time great heels if they let him)
Michael Cole - Heel commentator
Lesnar - Face (he's be as well being one after the Rumble)
Rollins - Face (His ring style would be better suited to being a face)
Reigns is going to have a long run as champ after Mania.
He'll obviously work programs with Rollins, Sheamus, Wyatt and Rusev over the belt but the one that I really think could be watchable, is when Ambrose turns heel on him and feuds with him over the belt.
Have Ambrose stop Rollins from cashing in MITB, and fights off the Authority with Reigns.. Roman turns around into Dirty Deeds. Good feud based on jealousy over the world title, and a much needed change for Ambrose with a heel turn.