The problem; is it that the cat is coming in or that it gets on your bed?
If it's that the cat comes into your room and you don't want it to and you have a lot of time this may work, my cat now doesn't go where she shouldn't unless she's coaxed (or bored and the door's open) into the area she's not to go, my cat doesn't have a problem with me for this method.
With my cat, to stop it going into the kitchen, I chose a point on the lino in the hall outside the kitchen and then waited with a wet hand when it got to that point (and only at that point) I shook a single dribble of water at her.
Though some cats like water, just to let you know.
Talking to the house-mate may help, though being gentle with them when talking to them is a givin.