Personally, I would avoid Welker because of his injury. Royal is a little safer bet, but it's not clear if Orton and/or Marshall will be starting. If Orton looks good and Marshall is out, I'd go with Royal. Otherwise (or if it still isn't clear by the time you need to set your lineup), I'd use D Jackson for your WR.
Because of all these questions, and since I tend to like RB in the FLEX spot, I would go with Mike Bell at FLEX. I'm pretty doubtful that Thomas will play, and it's unclear how much Wells will contribute at this point in the season.
Please keep in mind that I err on the conservative side. I'd rather get 5-10 points at my WR3 and FLEX spot than risk a 0 for the possibility of a big game. If you think that you need to 'go big', go with Wells and hope that he shines.
Thanks for the help on mine ( http://www.fantasyfootballcafe.com/forums/viewtopic.php?t=445153&view=viewpoll