The 26-year-old forward limped off during the second half of the Whites 2-1 victory over Western Sydney Wanderers on Saturday.
Roofe - who was pictured in a boot following the game - will now miss the opening few weeks of the new campaign through injury.
United initially feared a long-term issue but further assessment has returned a positive result with Roofe suffering a severe sprain.
Leeds will continue their pre-season preparations this weekend with a fixture against Serie A side Cagliari before kicking off the new season against Bristol City on August 4.
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The Whites still have injury worries over defender Luke Ayling and forward Tyler Roberts, who is yet to see action this summer, with the club yet to provide an official update on their condition.