Pepper has yet to establish himself in our team at SPL level and Meekings/Golobart were both physically a lot stronger which is one of the key attributes for SPL success.
While I agree with many comments the main issue with PR was his attitude in games, he never looked to motivated or interested, I think he has the ability but the pace of the Scottish game and where physicality is a more sought after attribute than skill and technique means its always going to be hard for that type of player - look at GMS or Ryan Jack they get kicked for 90 mins a game, although perhaps they are mentally stronger and can deal with that or used to it through the Scottish youth system.
Roberts may yet make it to a high level, look at the likes of Pennant (ignore his off-field issues and attitude problems) he was released by Arsenal yet has still played at a high level in England & Europe.
Roberts isn't tough enough. And pennant who is currently a free agent is a bad example as he played for Arsenal several times. Search up Sean McDermott. Rohn Ince, Junior Medes, Adam Coombes look at them