It is very important to oil the tray to roast them properly
I don't think it is a good idea to use olive oil, especially not extra virgin because the smoking point is lower. If you like olive oil, I suggest you add some at the end rather than when they are being roasted
Putting them with the flat part facing up is key to get them evenly roasted
Do not even think about adding the nutritional yeast before roasting them, nutritional yeast will burn
You don't need to wash them, in fact I don't recommend washing the brussels sprouts because you will add water to them and they may not roast as well. You don't need to wash them because they will get roasted so bacteria will be killed on that process. I guess you could if you feel they could have bird's... you know, but I am not worried about that. If you are doing it due to pesticide residue, let me let you, that's not a thing, we get parts per million which are not harmful to human health