Does roaming cause dropped calls?

A cell phone vendor in my hometown is attempting to dissuade people from signing up with Verizon or Alltel in favor of Appalachian Wireless which operates the only CDMA towers in that area. He asserts the following:

Is there any truth in the last part of his statement concerning dropped calls and ability to place calls?

Yes....of course there is truth to the dropped calls, but that really pertains to all phones with low signal strength, and not just because the signal is being bounced off another network's tower.

Not being able to place a call is basically the same thing as a dropped call. If you don't have a signal or have very low signal strength, you might not be able to place a call.

Thanks for the response bossdragon. May I ask for some clarification though? First, assuming that signal strength is not an issue, does roaming increase the likelihood of dropped calls due to the tower bouncing issue? Secondly, if you have two CDMA phones of the same model, one phone from Carrier X and one from Carrier Z, in an area of low signal strength conditions on Carrier Z's netowrk, would the phone from Carrier Z (in its home network) be more likely to get a better signal to make calls and/or have fewer dropped calls than the phone from Carrier X (roaming)?

Thanks again for your help.