Given Daryl Morey's tendency to wind up moving around in the NBA Draft, I'm going to be fairly broad with this first installment of potential Rockets' targets and perhaps narrow the list down to five or ten players come June. Remember, the Rockets have two first round picks (most likely at 14 and 23), so if I decide to throw a power forward into the mix at 21, it might be because the Rockets could have addressed their need at small forward at 14. Likewise, folks like Jan Vesely make the list because the Rockets could manage to trade up should they see something they like.
Also, the list of available centers in this class frankly stinks for Houston, since most of the taller players are finesse Europeans. Pairing one of those types next to Luis Scola wouldn't make for much of an intimidating frontcourt on the defensive end.
Assuming that each of the following decide to remain in the draft...
The Morris Twins
I'm not sure why I bolded and italicized the names that I did. They just seem like the most likely players to come off the board to Houston at 14, I suppose. Also, I really like Chris Singleton and Jordan Hamilton more than a few draft outlets do - Singleton especially, if only because he'd be a better fit in Houston than in many other places in need of score-first wings.
Good places to do your own research include Draft Express, NBADraft.net and Hoops Hype, and be sure to check out Chad Ford's pre-draft rankings. Ford is better at predicting slots than scouting players, but he provides useful information. Again, as we get closer to the draft, I'll add more analysis and go into further detail, but I thought it nice to at least list the notables.