Go Here for an official copy of Walgreens coupon policy
1. Register Rewards Do not Roll. This means if you purchase an item and receive a reward you can not purchase the same item and get another RR. For example if I purchase Dental floss and receive a reward I can not purchase Dental floss with that same RR. I would need to roll my RR into a totally different product.
2. RR are a Manufacturer coupon. You can not have more manufacturer coupon then items. For an example if I was purchasing Dental floss and had a manufacturer coupon and I was rolling a RR I would need to find a "Filler" items. The Caramels by the register are great for this. Or I usually look for an inexpensive item that is in the weeks ad for example the .50 baking soda or salt. You can however use a Manufacturer coupon and a store coupon together with no problem.
3. Only one RR will print per transaction. If you want more then one of the items that currently has a Register Reward you will need to do Multiple transactions.
4. RR expire two weeks from issuance.