  We investigate roaming in the photodissociation of acetaldehyde (CH$_3$CHO),
providing insight into the contrasting roaming dynamics observed for this
molecule compared to formaldehyde. We carry out trajectory studies for
full-dimensional acetaldehyde, supplemented with an analysis of a two
degree-of-freedom restricted model and obtain evidence for two distinct roaming
pathways. Trajectories exhibit roaming at both shorter (9-11.5 au) and larger
(14.5-22.9 au) maximum CH$_3$-HCO separations, characterized by differing
amounts of HCO rotation. No roaming trajectories were found in the intervening
gap region. The roaming dynamics near 14.5-22.9 au are well-reproduced by the
restricted model and involve passage through a centrifugal barrier, analogous
to formaldehyde roaming. However, the shorter-range 9-11.5 au roaming appears
unique to acetaldehyde, and is likely facilitated by repulsive interactions
absent in the simplified models. Phase space analysis reveals that this
additional roaming pathway is inaccessible in the reduced dimensionality
system. The findings suggest acetaldehyde's increased propensity for roaming
compared to formaldehyde may arise from the presence of multiple distinct
roaming mechanisms rather than solely the higher roaming fragment mass.
