Do they need to marinade in the dry rub before cooking?

They don't need to sit, if that's what you're asking. Simply rub them with the larger bowl of the spice mixture right before rubbing in and then wrapping the ribs with foil, right before putting them in the oven. If they need to sit a few minutes for the oven to heat, that's okay. There is no waiting period however between rubbing and roasting (steaming in the foil).
Hope this helps! ;o)