Roman Winter Campaigning

[Jona Lendering]

Did the Romans often wage war in the winter and did they do it deliberately or only when really forced to?

This is hard to answer. The early, middle, late Republic are different from the early, middle and late Empire.

Are there occasions when Roman armies deliberately attacked in the winter time as an element of surprise (like much later the Mongols with their winter attack on Kiev in 1240) ?

Yes. Germanicus' attack on the Germanic tribes in 14 was timed to coincide with a winter festival, perhaps Yule.