You can try hammering a triple square or torx bit into the rounded out head.  Worked for me on a Jetta pulley bolt that had rounded out.

Bill
------------------------------
 So I decided it was time to repack the CV joints and replace the torn boots.
 Got under the beast with a jack and hex-head socket. 4 bolts on the outboard
 side came off just fine. The other two are internally rounded (ie no flats
 for the allen to grab).
 Can't get Visegrips in there. Penetrating oil and/or a torch don't really
 seem to get to the threaded area.

 Any good ideas on how to get this thing out? I just got a set of Easy-outs
 so will give them a shot this weekend.

 Laurence
 '84 Westy