Most theory points to it being somewhat sensible to go wider in back for road.
There's more load on the rear tire, which a tire with more air volume and travel should handle better, both in rolling behavior and wear life. Aero effects are is also more significant at the front wheel, so potential aero penalties of wider are smaller in back.
Although, it doesn't seem to matter much either way, and staying the same front and back tends to be more stylish.

A lot of MTB folks prefer the opposite, wider in front.