Could we get Omer Asik? 
Do we have a young big you are willing to trade for him that Houston would want?
If Houston were to sign Dwight, they might be very interested in Sullinger. One of the reasons they're looking to move Robinson (other than cap space) is because he doesn't fit into the Rockets philosophy. Houston wants an offense based around one inside presence surrounded by 4 shooters and Robinson doesn't fit into that equation with Howard or Asik.
We forget that Sullinger isn't just an inside presence, but that he can shoot from the outside. Asik would be perfect for this team as it's constructed (with KG, Pierce, etc.), but unless they wanted a pick or (possibly) Avery, he's out of the price range that we should be willing to pay.
If non-guarantees or this year's 1st or next year's 2nd can't get Robinson or another one of their assets, you move on.