http://www.tirerack.com/wheels/results.jsp?filterSize=20&filterFinish=All&filterB rand=All&filterSpecial=false&filterNew=All&autoMak e=Honda&autoModel=Ridgeline&autoYear=2006&autoModC lar=&sort=Brand
this link will provide you with a number of 20in options including specifications on ofset ect and tire sizes you can even view them on your truck including your color
Tire Rack is OG so no worries and there prices are awesome. I do recommend you find a local Big O tire or some other place that will refill your tires with pure nitrogen as this will help ride quality and dont forget to check the alignment.
Also keep in mind that bigger rims are often heavier and move the weight out from the hub increasing braking distances reducing accleration and decreasing ride quality. Less than 80 pounds with wheel and tire each should be your target as this is the factory weight for the heaviest steel stock wheel and tire combo