\starttypescript    [math]     [xits][name]
  \definefontsynonym[MathRoman][file:xits-math.otf] [features=math]
\stoptypescript

\starttypescript[mainface]
  \definetypeface   [mainface][rm][serif] [termes][default]
  \definetypeface   [mainface][mm][math]  [xits]  [default]
\stoptypescript

\usetypescript[mainface]
\setupbodyfont[mainface,72pt]

\starttext
\startTEXpage
$\displaystyle\int^{xx}_{xx} XX$
\stopTEXpage
\stoptext
