Classic refers to the first version of the game.
1. 'Universal' game material. Supplements to add-in to other systems to give a greater amount of detail. Arms/Claw Law for combat, Spell Law for magic, and then Character Law for character development. I wonder how many people used these products in their D&D games...I'm sure the critical hit tables were fused into games in various ways if nothing else...
2. With the "main-points" of RPGs covered, this then is a system of its own, internally coherent. Iron Crown stopped printing information about converting Rolemaster data to the number-scales of other games, and began packaging the books together as a stand-alone system.
3. Middle Earth. Pre-MERP - Iron Crown got a license to publish works detailing settings in Middle Earth. What a coup! With time, a spin-off game is developed, 'Rolemaster-lite' (*heh*) in the form of MERP (along with other products). Rolemaster itself continues to be supplemented by Companion products, and also a campaign setting called Shadow World. New character classes are introduced, spell lists after spell lists are elucidated, the effects of unique herbs with strange names are detailed, more skills, more skills, more options...
4. Tolkien License revoked. Bummer. Can no longer publish the stats of the Steward of Gondor...Good thing they'd been thorough while the license held. One thing you can say about Rolemaster - thorough! They'd already detailed Moria, the Woses, the Court of Ardor, etcetera.
5. A continuation of #3 above. The numbered general supplements come to number seven. Companions are produced for each realm of magic, for two 'new' realms of magic, for alchemy, and for spell-users in general. Three compendiums of creatures and treasures. A companion book for character talents and skills, for warriors and arms-use in general, for war, for sea, castles, for constructs, golems and autoamta (I'm bouncing around the editions at this point...Rolemaster is still being published). The Shadow World setting never did much for me - but detailed settings have always been thought-experiments for me, I've never run a game with much of a mind to remaining true to a setting...but I liked reading Greyhawk, Earthdawn - Shadow World never jumped out and pulled me in.
Here's the thing. I tend toward 'low-powered' gaming. Limited information, limited scope. With the amount of detail in this game, I found it difficult to put on the blinders, and focus only on the aspects of the game that supported a low-powered campaign. If the characters were playing dumb grunts in the middle of nowhere (trust me, they weren't...), I was nevertheless aware that there were world-spanning organizations - there was magic that would allow amazing feats of communication and co-ordination - and this was distracting. (The fault here I lay at my own feet).
Yes, I'm going to have to go through the numbered companions next.