Brandy, I am a veteran CVSer now and I do love CVS and the ECB program. I recently started trying to learn WAGS (Walgreens). I have learned that the hardest thing is that their stores don't all follow the program the same way. I can go to several different stores in this area and get treated differently at each one. The big benefit to WAGS over CVS is that WAGS doesn't have any "card" so you can do unlimited deals - as long as they have the merchandise. At CVS you are limited in how many of the "Free" deals you can buy - no matter which store you go to.
Short answer: if you use an RR to pay for a purchase of another item that should produce an RR, the new RR SHOULD print as long as it's from a different company (product). For example, last week I was rolling deals on the Bayer Quick release 4 count ($2.49 w/ 2.49RR) and Ecotrin ($2.00 w/ 2RR). I could pay for one with the RR from the other (although I had to make sure the total was more than $2.49 when I bought the Ecotrin with the RR from the Bayer by adding a "filler" item. ( I just realized that I wrote "short answer" at the beginning of this fairly long answer... which just goes to show you that it's kind of complicated and I am long winded 
I am learning lots on slickdeals.net. They have threads in the "B&M Stores" (B&M means brick and mortar as opposed to online sales) that will let you see the deals, suggest scenarios and tell you which coupons are out there that you can pair up with the deals each week.
HTH!