True, but then a Rover is supposed to be a ticket that is valid for at least 3 days. There are some exceptions where products are erroneously called Rovers when they are, in fact, Day Rangers (W Yorks Metro Day Rover springs to mind).
Apart from Rovers (or a combination of Day Rangers), there is a Season that acts almost like a Rover and isn't too expensive either. Cattal - Conisbrough 7Day Season is £50.20 and allows travel by most lines within this area: York-Harrogate-Leeds-Wakefield-Swinton-Doncaster-Selby-York. (York & Leeds are both Appropriate Routeing Points for Cattal, and in addition to mapped routes, the shortest route rule allows travel via Pontefract Baghill, Moorthorpe & Swinton).
OK, so the area is a lot smaller than a Rover area, but depending on your requirements it could be an option for someone who wants to be able to travel before 0845.