Will changing my MTB crank-set (22-32-42) help me improve speeds on the road?

I have an 8 speed 11-32 cassette, and thinner lower resistant tires on my 29er, they are quality hybrid tires so I can still ride old railroad grades but no serious off-roading. I ride mostly streets in the foothills (a lot of up and down, and some nice long flats). Most of the bigger hills I can power through and seldom if ever go into my lower gears (1-8). Would a taller crank-set help me get more speed out in the flats? If so what would be a good crank-set for the foothill roads? 1-8 gears are a waste with my current crank-set. Any recommendations or guidance from you more experienced riders would be appreciated.