The final cut of TMC Podcast #29 is available now with topics time-stamped. We discussed the Tesla Cybertruck's expected 1 MW Ultra-Fast Charging capability, the Tesla Semi Delivery Event, the coming Model 3 refresh (project "Highland"), and more. You can watch it now on YouTube.
You don't say what kind of Model Y you are driving (what is your range at 100%?) or what kind of roof box. Really no one is going to be able to predict the drag caused by your roof box unless they have the exact same box and same car, but generally speaking the additional drag can be quite costly in terms of range.
If you want to play it safe, you could go through Detroit Lake on the way to Bend. It takes about an hour longer but with the additional charging stop, you won't have any issue making it. Also those roads might be safer in winter weather (of course depends on exactly where the snow and ice fall). It's a ~3300 ft elevation gain from Springfield to Bend. This will cost you roughly 33 Rated Miles. You will gain miles from dropping in elevation going the other direction. So if you make it to Bend, you'll definitely have no trouble making it back.
I saw almost a 30% increase from heavy rain and standing water on the road way (at 65 to 70mph). I expect snow will be as bad or even worse. 40% to 50% because of weather alone might not be out the of realm of possibility. Thankfully you could always slow down, and just by the nature of bad weather you might drop down to 40 mph or something vs 60 or 65, that will help some too.
I'd expect you'll be fine (assuming LR MY), but note that there are a few places to charge along that route, if you really get in a pickle, including in Sisters, OR. Take a look at plugshare.com before you head out...