"The Vagabond" is a lovely poem about the joys of a life of walking. In earlier centuries, it was quite common for people to take walking tours of scenic countryside; Scotland was a favorite place for walkers. Robert Louis Stevenson himself was a great walker often taking walking tours of Scotland. The hero of his short story "The Pavilion on the Links" is on a walking tour of Scotland when he falls into adventures and misadventures at an old school mate's pavilion by the sea. In "The Vagabond" the poetic speaker--and the poet--take the typical summer walking tour one step further and laud the joys of a whole lifetime of walking upon open byways (byway: a side road, not the main thoroughfare or highway).
In the first stanza the speaker summarizes the joys of the life he loves. He has the radiant sky above him ("the jolly sky": personification and metonymy). He has the byway right at hand near to him ("the byway nigh me"). When he sleeps at night, he sleeps in nature's natural bed and has the ceiling of the sky above him ("Bed in the brush with the stars to see"). For breakfast, he dips his morning bread in the fresh cool river instead of in a cup of coffee or tea.
The second stanza, also repeated as the fourth stanza, describes his sentiment that whether the storms (i.e., "blow": storm or forceful blast) of autumn come early or late, he wants the earth around him (not four walls) and the road beneath his feet (not a Persian carpet). He makes it clear that the only thing he seeks to have is the sky above and the road to follow beneath him. There are instances of personification and metonymy in lines one and three (personification) and line seven (metonymy).
Stanza three gives a sketch of the hardships of life outdoors in autumn: "blue" frostbite on the fingers; the silent birds; frosty fields as white as flour; the absence of a warm fireside sanctuary. Yet he insists that he will not yield to the cold of autumn--or even winter!--and will have "the heaven above / And the road below me." Personification is in lines one and four, which also has metonymy. "White as meal" is a simile, while "fireside haven" is a metaphor.