I usually do two 3-5 lb roasts together, but have done a single 10-12 lb roast.
I also use a big turkey roaster to hold all the veggies (covered) in the oven at 200-250 F. Every year I try to add a new vegetable - I'm up to 23 now. Start at 250, then turn down to 200 when adding the first roasts.
I stop the Showtime every 30 minutes and add the drippings to the veggies. To do 6 takes all day, so the slow roasting of the veggies does not destroy them.
After I shuck each roast, I bury it in the veggies. DO NOT add any liquid to the veggies, you will have an overflow. Also there is not much seasoning needed because it will leach from the meat and flavor everything. But, taste as you proceed and adjust to your preferences.
Another sneaky trick - refreeze the thawed roast for 1 hour to frost the outside, then use a fruit juce concentrate, or whatever steak sauce or marinade you want before adding the spices - they will stick to the meat while you attach the bacon.
I put the roasts on the rotiserie spikes and attach the top plate, then using toothpicks or metal pins ( I saved a bunch from some commercial bacon wrapped filets), attach the bacon like drapes from the top. Once all of the roasts have a bacon covering, begin tying the bacon to the roasts. I recommend pulling tight - the meat will shrink, and everything will come loose if you don't.
After inspecting all the ties, try loading the roasts in the Showtime. Turn it on, and watch for dangling bacon or places that need a little adjustment, and be sure all of the roasts are covered. Stop and make the necessary adjustments.
Whle the roast is cooking, I prepare the veggies and get them going.
You could - but I use our Bison roasts which are a lesser cut of meat. They are probably leg, brisket, or hump cuts. Many are prepackaged in butcher nets, so I know they surrounded a bone, or had excess fat that was removed.
If I were doing prime - I would reduce the time, and put in a preheated oven when I removed from the showtime. Remember to turn the oven OFF. It will continue to cook, but we prefer our prime rib rare, so just want to get it hot, not cooked through.
DIL makes GREAT prime rib in a standard oven. But our son says it is the only roast she cooks that comes out right. LOL
Probably because it is a very simple process - preheat oven, season and rack the meat, put in the oven, set the timer, let the oven turn off - then don't open or peek for the required standing time in the oven - usually 2-4 hours.
Got it for Christmas, met a guy and bragged about my cooking abilities, invited guy over for dinner, made shish kabobs. Shish kebabos could have been used for hockey pucks. Married the guy. Rotisserie is still sitting on garage shelf, never used again. The End.