Bushwhack up Roell Creek to Hidden Lake. Steep, rough, and ledgy, but I picked a good route. Traverse evil talus to Lost Lake. Ascend to saddle between Lost Lake and Irving Lake basins. Ascend up horribly loose talus to about 13,000', but forced back below saddle due to T-storm. Re-ascend up western sub-ridge then across SW face to join SE ridge. Easy ascent to summit... spectacular views. Descended along top of ridge all the way back to the saddle... much better choice. Camped at Lost Lake with some coyotes and elk.
Backpacked 10 miles from Beartown to Rock Lake. Climbed a loose, rocky, mostly 2nd class gully (not recommended) to gain SE ridge around 13,300 ft. Saw a mama bear and her cub at 13,000 ft while descending the SW slopes (toward Irving), apparently munching on something amongst the talus. A bear sighting high on Oso! How cool is that!
We camped at Emerald Lake, hiked N, and headed W and then snaked around the S side to summit. It seemed mainly class 2, but I recall huge boulders that let loose on way up from S. Next day we backpacked out 19 miles along W side of range.