These are the only rovers and rangers you can currently buy online:
GWR sell the following:
All Line Rover
Cherwell Valley Day Ranger
Cotswold Discoverer
Devon Day Ranger
Devon Evening Ranger
Freedom of Devon & Cornwall
Freedom of Severn & Solent
Freedom of the South West
Heart of Wessex Day Ranger
Kennet Day Ranger
North Downs Day Ranger
Oxford Evening Out
Oxfordshire Day Ranger
Ride Cornwall
St Ives Bay Line Day Ranger
Thames Rover
Thames Branches Day Ranger
Valley Lines Day Explorer
http://tickets.gwr.com/gw/en/journeyplanning/roversandrangers
Tickets are sent by 1st class post free of charge, they are not available TOD from stations. Tickets need to be purchased 5 days in advance or 2 days if you opt for special delivery at a cost of £6.
Southern sell:
All Line Rover
Southern Daysave:
https://ticket.southernrailway.com/search/other/daysave
Tickets are either sent by 1st class post or collected TOD from a Southern station. Tickets need to be purchased 3 days in advance for TOD and 5 days in advance for posting.
TPE sell:
North of England Rover:
http://tickets.tpexpress.co.uk/tpe/en/JourneyPlanning/roversandrangers
Tickets are sent by 1st class post free of charge, they are not available TOD from stations. Tickets need to be purchased 5 days in advance or 2 days in advance if you opt for special delivery at a cost of £6.
Southeastern sell:
Kent Rover
All Line Rover
https://ticket.southeasternrailway.co.uk/search/other/roversrangers
Tickets are sent by 1st class post free of charge, they are not available TOD from stations. Tickets need to be purchased 5 days in advance or the previous day if you opt for next day delivery at a cost of £6.