"Roller Skate Man" by Raymond Souster is about a physically disabled man who uses a board mounted on roller skate wheels to navigate through the streets of the city.
The author describes the "roller skate man" as someone who has a disproportionately large head, compared to the rest of his body, which is shriveled, with short "stumps" for legs. The device that this man has engineered symbolizes the man's independence: his ability to move freely through the streets of a society with others very different than himself. He wears gloves because he uses his hands to propel himself on Queen Street: the gloves protect his hands because the pavement is very rough.
The crowd that he "travels with" is made up of the successful and wealthy, symbolized by "silk stockinged legs" and "extravagant pleats," the fancy clothing he moves past. We don't receive any other descriptions because as the "roller skate man" moves, these are the only things his height allows him to see. Surely he is out of place socially with these people: especially as he travels in a world that does not see trees and beautiful store windows and fancy cars along his route. The symbols of his confined and lowly existence as he moves along are found in "spit, old [cigarette] butts [and] chewed gum."
The definition of "flotsam" is "useless or unimportant items; odds and ends" or "the part of the wreckage of a ship and its cargo found floating on the water." "Jetsam" refers to cargo that his thrown overboard to lighten a ship when it is in distress. When the author has described the man's method of transportation, and the kinds of people he passes and what he finds on the sidewalk, I get the impression that he is comparing the man to the well-to-do that he passes. It seems that the author is stating that because of his disability, people may see him as something "useless." The "roller skate man" may be the "wreckage" of a man. However, those he passes are seen by the author as what was intentionally discarded to ease the weight of a ship in distress. Perhaps he is saying that the "roller skate man" has elevated himself by adapting his physical limitations to the world so that he can get around, and most of the people on that street are just floating along as if they have been abandoned: both the roller skate man and those around him (the jetsam) are in the water: symbolically, neither group is in a good place.