Just my 2 cents, but here is what makes Walgreens hard:
1) The RR have to have the same number of items as rewards you are using. So, if you buy one pack of diapers and give over two $5 rewards the register won't allow it.
2) RR don't roll within companies. There are no limits since no card but if you do a P&G deal you can't use those rewards to get another set of P&G rewards.
Occasionally, they do roll though.
These two things alone make it harder for me to get deals as good as CVS or Rite Aid. I have only ever tried the deals once or twice but got frustrated with these limitations. Plus, since there is no card and never any limits the good stuff sells out at store opening on Sunday around here.