If you've mapped the stored procedure within the EDM Designer the appropriate procedure will be called automatically for update/delete actions on entities. More info on that here -
http://msdn.microsoft.com/en-us/library/cc716711.aspx.
Otherwise, a stored procedure which returns no data can be mapped within the EDM as a "query", and DevForce will generate calling methods for it within the EntityManager.
If the stored procedures aren't part of your EDM, within a server-side RPC method you can work directly with either the ObjectContext or Connection to call the stored procedure.