Well the way I saw it (being on Iorveths path) was that it wasnt an independent Temeria fighting Nilfgaard in White Orchard but just the local soldiers and patriots left over.
Radovid went mad and decided not to send his troops there and instead stayed stationed in Oxenfurt, thus no Radenian banners on the battlefield.
And Roche does fight the Nilfgaard much further south under John Natalis even if you took Iorveth´s path. You can see it in the megascope in the side quest with Cynthia.
At the end of Witcher 2 on Iorveth´s path, when Temeria is divided between Henselt and Radovid, Roche is inspecting whether Nilfgaard is about to attack with John Natalis´s unit.
He was inspecting the border, not fighting for free Temeria.
John Natalis sent him there before the summit at Loc Muinne so he did not know what the outcome would be yet.
And as it happened, Nilfgaard did attack and Roche and his unit lost and he returned to Oxenfurt.
Radovid went mad and decided not to send his troops there and instead stayed stationed in Oxenfurt, thus no Radenian banners on the battlefield.
And Roche does fight the Nilfgaard much further south under John Natalis even if you took Iorveth´s path. You can see it in the megascope in the side quest with Cynthia.
At the end of Witcher 2 on Iorveth´s path, when Temeria is divided between Henselt and Radovid, Roche is inspecting whether Nilfgaard is about to attack with John Natalis´s unit.
He was inspecting the border, not fighting for free Temeria.
John Natalis sent him there before the summit at Loc Muinne so he did not know what the outcome would be yet.
And as it happened, Nilfgaard did attack and Roche and his unit lost and he returned to Oxenfurt.