  We explore the relationship between multigraded Castelnuovo-Mumford
regularity, truncations, Betti numbers, and virtual resolutions. We prove that
on a product of projective spaces $X$, the multigraded regularity region of a
module $M$ is determined by the minimal graded free resolutions of the
truncations $M_{\geq\mathbf{d}}$ for $\mathbf{d}\in\operatorname{Pic}X$.
Further, by relating the minimal graded free resolutions of $M$ and
$M_{\geq\mathbf{d}}$ we provide a new bound on multigraded regularity of $M$ in
terms of its Betti numbers. Using this characterization of regularity and this
bound we also compute the multigraded Castelnuovo-Mumford regularity for a wide
class of complete intersections.
