Refining my roast beast technique

My latest experiment is to see if I can use a single oven to have a roast and baked potatoes come out with convenient timing for everyone to dine without any reheating, and to produce a good gravy from the drippings. Here is the procedure I used, annotated with the details:

1. Begin with top round roast; this one was 5.90 lb. (An entire top round can run 10–18 pounds.)
2. Coat roast in seasoning mix [8:3:1 Montreal Steak Seasoning : coarse ground black pepper : garlic powder] the night before cooking, wrap in foil, let it sit in the refrigerator. (The goal with the seasoning is to cut down on the sodium that drips into the gravy; otherwise I would have just used straight Montreal Steak Seasoning.)
3. Bring out roast in the morning and let it warm gradually on the counter.
4. Preheat oven to 200°F. Line a deep roasting pan with sliced mushrooms and quartered onions. Pour in low-sodium beef broth. (The drippings should carry the seasoning in to spice it up.) I used an entire 32oz. container, enough to actually float the mushrooms, and that did not reduce so far as to become gravy by the end— there were 20oz. left after I scooped out the onions and mushrooms, and obsessivewoman used it as a substitute for water with a gravy mix. The mushrooms were quite tasty, but the onions weren’t entirely cooked. Next time, I want to try about 16oz. of gravy, and slice the onions into discs so they are fully submerged.
5. Sear the roast, place on rack, insert thermal probe, place in oven. Set probe alarm for 110°F.
6. Monitor beef broth level and top off as necessary. (This proved to be unnecessary.)
7. Prepare potatoes for baking by piercing with fork, coating with olive oil.
8. When the probe alarm goes off, crank the oven to 500°F, insert the baked potatoes, reset the probe alarm to 130°F.
9. Remove roast when the alarm goes off (moving thermal probe to a potato and resetting it to 210°F) and allow it to rest for half an hour in foil to retain heat. Serve appetizers, e.g. salad.
10. Remove baked potatoes when the alarm goes off.

Observations:

• The roast was tender and flavorful, mostly medium rare with some medium around the edges.
• The potatoes were in a pan rather than on a rack, and they sweated. A lot. They were in boiling puddles as they were cooking. My hypothesis is that the roast had already saturated the air within the oven so the water from the potatoes had no place to go. Next time, I want to put them on a roasting pan to catch the water, and see if we can turn the convection on for short periods of time to dissipate the humid air. The potatoes’ water was obviously boiling while the broth was barely simmering, probably due to proximity to the heating coils. The potatoes wound up fluffy on the inside, but steamed on the outside rather than crisp.
• Either the broth or the potatoes (and boiling of the water from them; probably the latter) slowed the transition from 200° to 500°; the oven was only in the mid-400°s before the meat hit 130° internally. Next time, wait for the oven to hit 500° before inserting the potatoes.
• Steam transfers a lot more heat than air; stand back when you open a hot oven with something simmering inside!
• Temperature and timing:

  14:38	59°
  15:35	76°
  16:35	105°
  16:44	110°
  17:27	130°