The 22-year-old, who has yet to make it onto a World Cup podium, descended the Planai course quicker than his rivals with the session cut short to avoid clashing with the finish area of the slalom run of the women's super-combined event.
Slovenia's Andrej Sporn had the second best time 0.33 seconds adrift, with US skier Marco Sullivan 0.48 behind Roger.
Out of the top downhill contenders ahead of Saturday's race, Austria's Klaus Kroell was the fastest of the pack in fifth place, 0.69sec off Roger's time.
Reigning downhill World Cup winner Kroell heads an Austrian team hungry for medals at these world championships on home snow, after coming up empty-handed in the men's and women's super-G races earlier in the week.
Kroell is one of six favourites for the downhill, alongside compatriot Hannes Reichelt, Italians Dominik Paris and Christof Innerhofer, Norway's 2007 world champion and Olympic silver medallist Aksel Lund Svindal, and defending downhill world champion Erik Guay of Canada.
Saturday's downhill will see the skiers hurtle down a 3,282 metre icy course at speeds approaching 75 miles per hour.