Oh, if that's what you want to do (and you're the type to dig a snow cave in winter), ride up Foresthill Road all the way to the end, past Robinson Flat, to Soda Springs Rd. Soda Springs Rd will then take you to Soda Springs at I-80 and you can take the "Hole In The Ground" trail passed the Snow Lab to Boreal, then up to Castle Peak.

I've never been on Soda Springs Rd, but back when I had a dual-sport motorcycle I understood that it was ridable. I know Sean Allan on mtbr.com has posted about a lot of his rides in the general area (Foresthill to Truckee, Foresthill to the Rubicon Trail/Tahoe), and if you're willing to ditch skinny road tires, I bet it'd be do-able.