As a noun, troop means (1) a group of people, animals or things, (2) a group of soldiers, or (3) a great many. As a verb, it means to move in a group or as a crowd. The meaning of troupe is much narrower. It denotes a company or group of actors, singers, or dancers.
These writers use troop correctly:
Not all troops and troop leaders, however, welcomed the Colorado decision. [Huffington Post]
Thousands of Minnesota soldiers are preparing for the state’s second largest troop deployment since World War II. [My Fox 9]
On Feb. 26 many of the same stars will troop to the beach in Santa Monica for the Film Independent Spirit Awards. [NY Times]
And these writers use troupe well:
Last Minute Low Budget Productions is a non-profit community theater troupe based in Terlingua. [Alpine Avalanche]
Everyone’s favorite youth Kabuki troupe has finally returned to the airwaves after a long winter’s nap. [Gawker]