I know nothing about the Troy area.
Darby is a great little town. You'll have the whole Bitterroot Valley at your feet, with for all-purposes endless options.
Blodgett Canyon is a nice, though crowded, hike. You can do as long and out and back as you like. Quite rocky in spots.
Hiking to the summit of Trapper is also a worthwhile outing, and gives one of the better views of the whole area.