If it's under warranty, get Microsoft to ship you a replacement box to send yours back in.
In the meantime, take your 360, wrap it in towels or blankets (I just stuffed mine under my bed sheets), and run it for 15 minutes. This "towel trick" is a temporary (yes, only TEMPORARY) fix for your RRoD problem. It will at least allow you to start playing the game before you can get a new console.
Mine gets RRoD all the time, got it from a friend because it was broken, so I have to keep fixing it. Hopefully I'll get a new 360 soon when the new motherboards come out.