Canny!

The first thing Rufus did was to turn his music to high volume (to drown things out). Then he beckoned Roger to sit on the bed (out of sight) and grabbed a can of beer from the shelf and threw it to him (to get him offguard and distracted!).

It wouldn't have improved the beer except to make it explosive!

But Roger wouldn't be drinking it anyway!

While Roger was busy catching the can, he missed seeing the fist heading straight for his face as Rufus leapt forward. The thud knocked Roger clean out; it was one of Rufus's specialities.