I haven’t seen a Red Robin coupon in a while!
Right now on their Facebook page  you can get a coupon for $5 off of $20.
Just click on their wall where they talk about the coupon and they will e-mail it to you.
Here is the fine print:
Good for $5 off a $20 purchase. Valid only at participating U.S. Red Robin® restaurants. Minimum purchase required. Not valid for the purchase of gift cards or alcoholic beverages. Tax and gratuity excluded. Dine-in only. Limit one coupon per check per day. Cannot be combined with any other offer except Red Royalty. Not valid at Red Robin’s Burger Works locations.
Coupon expires September 3rd.