Yes, there is a right to roam
Actually, there isn't.
There is a right to be able to walk a designated RoW, and there is a right to walk anywhere on land designated Open Access Land (the majority of which is upland country). In both cases, there is a duty not to cause damage. Otherwise, even on "permissive" routes, no "right" exists.
The phrase "Right to Roam" is one of the most often quoted and misunderstood phrases in walking. It both misrepresents the rights of the walker and is guaranteed to raise the blood pressure of any farmer/landowner, and usually ends up causing disharmony where once peace existed. I get the local dog owners round my way bleating on about this because the local farmer has had the gall to ask them to keep to the paths!
In situations such as ploughed-over paths common sense must prevail. The farmer has a duty to reinstate within 14 days, although well-used paths probably won't need reinstating anyway. Like most have concluded, the easiest way is usually the best way - through the field if it's clear, round the edge if not.
Lets leave the work and the confrontation for when it is really needed, and give our beleaguered RoW teams and farmers a break!