Indeed one room and up to 2 other rooms. You must pay for all the rooms you want to earn points for.
So I would suggest you arrange this with colleague that he pays the room to you and you pay both rooms to the hotel.
Be sure to mention upfront during check-in that you will pay for both rooms.

Alternatively, if this arrangement with your colleague would not be possible you can also refer him : http://www.marriott.com/marriott-rew...er-a-friend.mi
Through a referral you will earn 2000 points per stay for the fist 5 stays your colleague does. (and he will get these 2000 points as well)