Freedom in the whole-arm string crossing action is important as it supports clear articulation and resonant tone production.
Rolling across the bridge means we can focus on the freedom of movement without thinking of the notes we need to play.
When playing on the open strings make a continuous roll across from the G string to the E string. Then add in left-hand fingers with for example the G minor arpeggio, which encourages an even, smooth string cross as it has 2 notes on each of the G, D and A strings.
Of course we will need to vary the speed of the string-crossing action in the repertoire when the number of notes on each string is not regular.