We're hoping to end a Venice trip with a few days in the Dolomites around the first of November. Is that too late in the year to do things like the Alpe di Siusi? Would there be snow on the roads?
Yes, too late. Too late for summer and fall activities, too early for skiing/winter activities. Many lifts are closed, buses on limited schedules. Driving in passes likely requires traction devices.
We're traveling in early October and found out that many places close end of Sept to early Oct. Things open back up in December. There are a few places open year around, but most things will be closed in November.