The bumps you get from the late season promotion are coachable bumps (splits, ground ball, contact, glove eye, control, etc.). The bumps u get after rollover are training bumps (arm, power, velocity, speed, etc.). So, if you do not use the late season promotion strategy, will not see any late season bumps to coachable ratings.
Keep in mind that not all players will get bumps. Sometimes, especially when the team does not make the minor league playoffs, a player will not see any coachable ratings despite the promotion. Players will have a higher probability of receiving bumps if they have more games played (ie playoffs).
Also, have to be careful with demotions, if a players patience rating is low, he could receive a ratings nerf.