"The Road Not Taken" by Robert Frost is not a purely imagist poem, and thus the emotions are conveyed as much by overt use of emotional terms as implicit within the poem's imagery.
The first image which creates emotions is that of the "yellow wood". Autumn, because it marks the end of summer and the death of vegetation in temperate climates, is often associated with melancholy in poems.
The description of the roads as not being worn and the leaves as not being trodden black suggests that the narrator views this wildness as something positive, or as an opportunity for exploration, although the images of the roads as unspoiled by human feet also suggest solitude or loneliness.
The images of roads diverging suggests that choices made cannot be taken back, and thus evokes a sense of regret that of the possible roads the narrator can only take one.