Why would my ankle swell and bruise a week later after a knee injury on the same leg?
You fell! You might have twisted the ankle, broken the ankle and due to the immediate problem: knee, did not know it let alone notice it. I assume you were wearing a boot when rollerblading, so that could have protected the ankle and only now after all this time, has the damage been revealed. I would do what the Doc told you to do, just to be on the safe side.
