I run Shimano roller brakes front and rear on my Redline R530, other than staying away from the ones with the "modulator" (not sure what models) they work just fine. Me and the bike weigh in around 275#-300# fully loaded and I can haul down from a 15mph cruising speed very quickly regardless of the weather conditions, they modulate easily and I can lock the wheels at lower speeds.
FWIW in sluggo's case I suspect it isn't adjusted properly or something is worn.

Aaron