If it is newly unrolled I suggest using the grain of the fabric to cut the fabric, perhaps leaving enough extra to be able to hem it, just in case, then wet the fabric and hang it by the selvedge. Fold it carefully to whatever length of washing line you have and use lots of pegs, then let it hang and drip - hopefully the twist will come out.
If you plan to pull it straight, spray it to damp it first, then keep the cloth straight as it dries.

The teacher at school who took us for sewing was adamant that skewed fabric was permanently twisted - after three washes the twist was gone and every seam in the blouses we made was slanted.

Anne the Pleater