Fighting up to the age of mechanisation was conducted by all sides in "campaign seasons" when the snows melted and enabled movement of troops, artillery, cavalry and supplies. The Romans no exception. Armies dug in and biovaced in local towns for winter in ready made garrisons or in exceptional cases the fields. Reference Napoleon in 1812 who expected to have won my the end of the season, but lost 95% of his army of 600000 by miscalculation. Again, mechanisation was and still is not the silver bullet. In 1982 the British campaign was days from failure due to the weather closing in. Per the question, Roman armies carried significant engineering equipment and had both experience and training, but heavy snow would reduce March distance by day to 5 miles or less depending on conditions. The equipment carried was shovels "vatlillum" per man made of iron, these were intended for entrenchment and reverts rather than clearing snow. Light snow would significantly affect an armies march. Heavy snow prevents it, even today with tracked vehicles.