DJAFFAR AL KATANTY WHEN the Nyiragongo volcano erupted in May, Serge Makolo only had time to grab his roller skates and a fistful of medals before the magma swallowed his house on the outskirts of Goma in the eastern Democratic Republic of Congo. Everything else was lost under the river of molten rock, including the skates, cones and helmets he used to train younger skaters, whom the 24-year-old calls "world champions of tomorrow." Makolo, a medallist at several local and regional meets, is eager to win more competitions so he can get money to rebuild his academy, whose recruits currently…