Basically you shouldn't have any problems returning the result of a stored procedures via your RIA service. What you need to do is expose it like you normally do with your other endpoints. So for example if your stored procedure returns customers then you will need to add the following:
Please note that in some cases the data services themselves cannot correctly "guess" the primary key of the object you are returning. In that case you will need to go to your persistent class and mark its primary key with the [Key] attribute.
I hope this helps. Please do not hesitate to contact me back should you have any further problems.
the Telerik team
SP1 for Q3’11 of Telerik OpenAccess ORM is available for download.