ROOT comes with TTF fonts.
They should be somewhere in “${ROOTSYS}/fonts” or “${ROOTSYS}/share/root/fonts”.
Have a look at your “${HOME}/.rootrc” and your “root-config --etcdir/system.rootrc” and check the settings:
Unix.*.Root.UseTTFonts: true
..Root.TTFontPath: /full/path/to/the/ROOT/subdirectory/with/TTF/fonts