You understand the difference between something that's not very nice and something which someone cannot possibly eat at all, right? As a vegetarian, I can imagine some pretty gross combinations of pizza that I still can eat, but I'm at a massive disadvantage if I get something I cannot eat at all.

It would be a pizza-loot-box. That actually sounds like a nice product.

The whole idea of potentially unpleasant or not consumable (due to allergies) output is a problem for me. The waste in time, work and resources to output something that has a high likelihood to be discarded (pizza is perishable) isn't something that should be encouraged. Especially when there are steps the service provider could take with minimal effort to avoid that outcome.

Typically with roulette there is a substantial upside to winning as well (large payout at casino for example). What is great thing you get by winning pizza roulette? A pizza that you could simply have ordered at no risk?