I'm not really sure about Riddell yet, I like some of his running from dummy half, I'm just not sure if other players are on his wavelength yet, I think your spot on though. A decent run of form might do him the world of good!
I like Roberts so far, he looks exciting in open play, I'm not convinced about his catching though, doesn't look great under the high ball under pressure. I can't wait to see him go the length of the field, I haven't seen someone in cherry and white do that properly in ages. Calderwood did, but not properly, he rarely had to beat men to do it, he needed to have nothing infront of him at all.
*Edit* I've changed my mind, I like Roberts alot, just for smashing Gilmour
awesome hit from a winger on a second row