Attending one of our ROW training sessions will help you to understand what this is all about.
Your starting point for Herts http://webmaps.hertsdirect.org/row/row.htm
This one looks like a work in progress but may ultimately tell you which of the above you cannot use. http://webmaps.hertsdirect.org/tro/tro.htm
This one shows the unclassified roads http://www.hertsdirect.org/actweb/gazetteer/default.cfm
Central Beds Not working very well http://www.centralbedfordshire.gov.uk/onlinemapping/map.aspx
This unofficial map shows Rights of Way based on downloadable GIS. It does not have information regarding TROs or other restrictions. http://www.rowmaps.com/