Is it possible to visit Assisi and Sienna in the same day without feeling rushed? We will be day-tripping out of Rome.
I personally think so. You could easily spend a whole day in each to see the main sights.
I'm voting NO if day-tripping by train. You'll have 8.5+ hours of train travel and that doesn't include time from train stations to center of towns. Even if you left at 07:30 and got back at 23:00, you'd have 3 hours or less in each town and that would feel rushed to me. Siena and Orvieto would be a better option for 2 towns in the same day.
I would strongly recommend not attempting both Siena and Assisi in the same day. First, it's 2.5hrs to Assisi from Rome. Then, you have to take a local bus to and from the town. Then, it's a 90-minute train trip to Siena and once again, a local bus ride to the town (unless you want to walk almost a mile uphill). Then, it's 3.5hrs back to Rome on the train. Plus the waiting time at bus stations and train stations and you have over 9.0hrs - maybe 10.0hr. Each is really worth one long day to visit. So much to see in each town. You will be rushed if you try both in the same day.
Even TWO separate days I would feel rushed (especially in Siena which is one of our favorite towns). I'd agree with Frank & Larry; the travel time is too excessive. Suggestion: slow down or make a choice of which you must see! Good luck!
Ciao,
Ron