"Looking at the topo now...is there a pretty obvious route from Roosevelt to Young lakes?"
Going directly southbound from Roosevelt Lake, you can descend down into a valley and then ascend back up. There's no future in that.
Instead, start out southbound and then contour around the hillside eastward along the 10,000 foot line, all cross-country. That ought to land you at about the Middle Young Lake. As it turns out, that is normally the best of the three Young Lakes. The Lower Young Lake is the big one, and it is normally reached first by beginners arriving from Tuolumne Meadows, so that is where they drop their packs. The Middle Young Lake is at 10,000 feet, and it is smaller and less overrun by beginners. You can also camp at the Upper Young Lake, but on a normal year it is mosquito-infested. This year, it's hard to tell. There are very few trees at the upper lake, so there is not much cover in the event of a storm.
As long as you are going basically south, you will hit one of those three lakes. If nothing else, as you are moving south from Roosevelt Lake, you can sight on Ragged Peak which stands prominently above the lower lake.
Now, if you try to change everything and go in the reverse direction, you will have to get a permit for the trails from Tuolumne Meadows to Young Lakes, and that is a tough one to get! Also, since that is a tough one, there are people who try to do that trip without the benefit of a permit. That's why the NPS rangers are often roaming about, to check permits. In fact, the rangers used to get such a hard time from some backpackers there that the rangers had to carry sidearms. I've seen some interesting law enforcement interactions around there.
Incidentally, if you find yourself around Young Lakes and have an extra day to kill, there is a good layover day hike. From there you hike up Mount Conness and return. It becomes boulder scrambling for the top 200 or 300 yards. Once in a great while there will be some snow on that last section, but probably not this summer. If you slip on the snow, it will be the boulders that will kill you.