ahh yes, getting them to go to their rooms. A difficult one once they are too heavy to lift up the stairs, though you'd be surprised how much writhing and kicking bad boy weight I have firmly carried up the wooden path to bedsville when I have been pushed to my limits....
Www, hope you don't see this as a cop out, but what I do is threaten to phone daddy if my son won't go to his room. In our house this works. I hasten to add my husband is not an ogre but has a loving relationship with my son. Alternatively, I have threatened to tell his headmaster or class teacher. If my son tries to come down the stairs once up, I repeat these threats. I have had to phone up dh sometimes. Remember, you can always 'fake' a phone call if there is no person at the other end.
As Mollipops has outlined, a progressive threat to withhold a favourite toy is also very effective.
IMO it is really important to get your son to do as you say, and accept a suitable punishment/time out when he is being mega difficult - and keep your temper while doing so.
I say to myself when I feel like the witch mother from hell, if I'm not firm now, what will happen when I face a misbehaving 11 year old? He'll grow up thinking he can get away with everything. Also, once up in his room, the benefit is immediate. Nine times out of ten, when I eventually call him down, he is much calmer.
BTW, IMO that's one small problem with threatening to withold a toy or treat - in the short term, it winds him up. He needs space alone to change his mood. I sometimes think he feels like a runaway train - he actually wants to stop being bolshie, but while he's facing me, he can't do this.