On 5/16, we made it to about the 4 mile mark (3 miles past the designated trailhead in Roach's book) in a stock Jeep before we ran into some large boulders in the middle of the road. The stopping point for us was right at a turn which has a parking area big enough for 3-4 cars.
About 0.25 mile up from that point, there were a few snow fields that would have stopped us had the rocks not. There were patchy snow fields and standing water through the wooded sections of the road. About 0.5 miles past the plaque, the snow became pretty consistent on the road and we used snowshoes up to the lake.