Roasting more than 1 meat in using one oven
If you have room to place the Wellingtons on the same shelf, you simply cook them in the same way as you would a single one. Conventional ovens do not work like microwaves - the amount of stuff in the oven makes no difference, providing air flow is maintained and you don't have something large right up at the top or bottom blocking an element.

Fan ovens are especially useful as they actively circulate the heat around the oven cavity, so you can cook things on two different levels with fairly good consistency.