Per the "Mr & Mrs Roto-Broil Cookbook"
Once you have the bird trussed and properly positioned on the spit (balancing it can be a challenge), mix some (olive) oil and garlic and brush the bird.
Roast on "Medium" for 30 minutes, bump it up to "High" for 30 more minutes, then back down to "Medium" for 20 minutes or until done (usually 20 minutes will do it). The book advises to brush the bird again at each temperature change, but I have found that to cause flare-ups and the bird bastes itself fine anyway.
I usually select a 5-pound chicken to roast on mine and they turn out fine with the above recipe. If you use a smaller bird, keep an eye on it during the final segment. I wouldn't do it for longer than 20 minutes.
I follow the roasted capon recipe out of the above referenced cook book. The books turn up fairly regularly on eBay.
We were just out at the "Electronic Goodwill" in Tucson yesterday and they have a Roto-Broil Riviera 400 there complete with literature, but it had no spit. An interesting looking model, but apparently bottom of the RB line.