Spinach
Make sure that your spinach doesn't have too much residual water. Try and use prewashed dry spinach.
Pasta
If you don't have rotini pasta on hand, use any bite sized pasta like penne or shells. Cavatappi or cellentani noodles or elbow macaroni noodles will also work well here.
You can change up the recipe by Changing the kind of pasta
The formula for Pasta is
Time= {(time on the package)/2}+ 1 minute