Actually, since all that Rammus deals out is Magic Damage, he indeed does need the Magic Pen marks to help him out. Especially since marks specialize in attack rather than health, so it is a more effective use of those slots. I already take Quints of Fortitude and Seals of Vitality, which in my opinion more than cover the need for bonus health.

No need for magic pen marks get some health ons insted much better on rammass. and you build frozen heart first go with a thornmill much better trust me i kinda have to main with him a lot