If there is no botulism or other bad bacteria present in the ranch sauce, the temperature doesn’t matter.
If there is botulism or other bad bacteria present in the ranch sauce, the temperature doesn’t matter, either.
Perhaps you are thinking of situations like, say, a picnic, where there was ranch or mayo that got warm in the sun and bacteria grew in it and got people sick. Remember that time is a factor here – if it sits out for a long time and bacteria grow, you’d get sick. But it’s not necessarily that the ranch got warm, it’s that it stayed lukewarm for long enough to support, uh, life. Just warming it up in the oven won’t do that, assuming you ate it immediately. Just don’t leave it on the counter overnight and eat it, or anything silly like that.