From the trail head at Carson Pass head south on the Pacific Crest Trail for about 3 miles. The trail passes Frog Lake (probably will not see it behind a small rise) and then contours along the base of Elephants Back and gently rises to Winnemucca Lake. From here the trail turns west and rises up toward Round Top Lake. As the trail crests a ridge and Round Top Lake comes into view it is time to turn left and start your main ascent.
An approach can also be made from Woods Lake off S.R. 88. From the parking area head up the Winnemucca Lake trail for 1.5 miles to the lake and its junction with the trail from Carson Pass. Turn right (west) and follow the trail toward Round Top Lake.
There is another trail on the west side of Woods Lake that takes you directly to Round Top Lake.
From the approach trail there are a couple of climbers trails. One goes over the small rise headed southeast and one skirts around it. Once around this small hillock there is a large open scree slope. There is often a large snow field here even well into summer. Be carefull near the middle of the snow field as there is a snow melt stream nder the snow there. Head up this slope toward a saddle between Round Top and The Sisters, a set of craggy volcanic peaks right above Round Top Lake. Once the saddle is gained the fun begins. From here a little route finding is in order and one can pick their own line to the summit. The best route is a little to the right of the main ridge. The slope is about 30 degrees just before reaching the west side of the summit crags. There are two summits: west and east. The east summit is the high point. Climb class 2-3 rock to west summit, then descend to the gap between the two. Traverse around the east summit then climb it from the SE side.
For a summer time climb some good sturdy foot wear is all that is needed. If a winter climb is in your plans. Cross Country skis or snow shoes are in order for the approach with crampons and ice axe for the summit. The glissade down to the northeast towards Winnemucca Lake from the saddle is great if the snow isn't too soft.
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Calling the West Ridge a "walk-up" is misleading. It's Class 2 until you get to the West summit. Getting from the West summit to the East (true) summit, is the crux of the route, and if you haven't made it to the East summit - well - then you haven't summited Round Top, sorry guys...
Getting to the summit involves negotiating very loose scree slopes, some with undesirable, cliffy runouts in the distance. How confident are you in stopping a slide on scree? It also involves Class 3 (the route we took was more like Class 4) scrambling on rock to mount the summit mound with virtually no protection opportunities, and it's not unusual for your foothold to give way or for your handhold to find itself sitting squarely in your hand, no longer attached to the rock, if you don't pick and test carefully.
There is a rappel/belay pole a few steps down from the summit marker if you want to make your descent safer and skip the crux downclimb. I bounce tested it and it seemed solid. The rappel is low angle/load too. A 30m rope is enough to get you past the difficult section, almost to the base of the summit mound.