well it depends on which uav we are talking about. The 2 that I know that can carry weapons are the predator and the reaper. Predator is the smaller one with less room for weapons, lower altitude and is used mainly for recon stuff.
Reaper is the larger one (almost as large as some of the modern fighters) with more room for weapons. Reaper is also significantly faster due to a more powerfull engine, which also gives it the ability to fly higher.
And about the weaponry, well it's not that awesome. Predator usually just has 1 or 2 hellfire missiles. Reaper I'm not too sure about, but it has more firepower than the predator.
And there might be just one guy guiding the drone, but you also need people for the other air vehicles, ground station, communication etc.
I'll try to find the text.
"The MQ-1 Predator is a system, not just an aircraft. A fully operational system consists of four aircraft (with sensors), a ground control station, a Predator Primary Satellite Link, and approximately 55 personnel for deployed 24-hour operations.
The basic crew for the Predator is one pilot and two sensor operators."
from
http://www.af.mil/factsheets/factsheet.asp?fsID=122