  The Rosen fractions form an infinite family which generalizes the
nearest-integer continued fractions. In this paper we introduce a new class of
continued fractions related to the Rosen fractions, the $\alpha$-Rosen
fractions. The metrical properties of these $\alpha$-Rosen fractions are
studied. We find planar natural extensions for the associated interval maps,
and show that these regions are closely related to similar region for the
'classical' Rosen fraction. This allows us to unify and generalize results of
diophantine approximation from the literature.
