With some tickets if you cannot complete the journey in a day, you can break your journey overnight and resume the next day, however I don't think this applies to Rover or Day Ranger tickets.
By definition, Rovers are more than 24 hours as they are multi-day tickets valid for at least 3 days and count as 'Seasons' for the purposes of Condition 19 of the National Rail Conditions of Carriage.
Day Rangers are only valid for one day. The railway ticketing day ends at 0429.
(There are some Day Rangers that are erroneously called Rovers, such as the West Yorkshire Metro Day Rover. They should be called Day Rangers)