The message
from Tristan Hatton-Ellis contains these words:

Rocket is perfectly, hardy, so it may well be possible to grow it as a
winter crop. In fact, the cool temperatures should stop it bolting, which
tends to be a problem in summer, so you may actually get bigger plants.

That may be the case further south, but here (Scotland) edible rocket,
arugula, is an annual which invariably dies completely before winter.
Nor does it self-seed itself here the following spring ; IOW it's far
from "perfectly hardy".

You may be thinking of "sweet rocket", hesperis matronalis..a taller
coarser much more robust biennial or shortlived perennial cottage garden
plant grown for the white or mauve scented flowers, not for salad
leaves. That's much hardier, usually survives normal winter temps here,
and selfseeds itself everywhere.

Janet.