When I let an oil marinate, does it have to be in the fridge, or can it be room temperature?

Good question.

Hard question to answer absolutely.

There is a temperature range through which foods can be allowed to stay at for a limited amount of time---and then you can have a real problem with bacteria multiplication and potential food poisoning.

Here is one site that states unequivocally that all marinating must be done in the refrigerator.

https://whatscookingamerica.net/MarinatingSafely.htm

Here is another which has some good advice and a lot of opinions. This site gives a lot of what I would call "common sense" answers; and I tend to agree with them.  "Common sense" is usually good enough to prevent food poisoning.

https://www.chowhound.com/post/refrigerate-order-marinate-655587

Until you gain some experience, I would tend to eerr on the side of caution, however.

If you're marinating meat, leave it in the fridge.