As Japeke found out and posted in the Run2Roxette Forum, Roxette will indeed be part of the Nokia Night of the Proms.
This is the way Japeke confirmed the news we already believed in since two weeks now:

If you go to, and then click on germany, netherlands or belgium (Antwerp), just click on program.
If you rightclick on a photo of a artist, you get a specific adress, like

Try what you get if you replace ‘sharondenadel2’ by ‘roxette’, so you get A picture of roxette in the folder of the artists which will perform in 2009!!!!!!!!!!!!!!!

It doesn’t work for charleroi, france and Spain, but it does for Antwerp, Netherlands, and Germany. So I would say: START BUYING TICKETS Cheesy Cheesy Cheesy Cheesy

Source: Run2Roxette Forum, thanks to Japeke!