A DVD-ROM is normally stamped, not burnt. However, with DVD+R media, you can specify the booktype on the DVD during the burning process with some burners; if you specify a booktype of DVD-ROM, any DVD player will then think the DVD+R is in fact a DVD-ROM - be aware though that you've not really created a DVD-ROM (because DVD-ROM's are stamped), you've only fooled the player into thinking it's a DVD-ROM; all of the other characteristics are still that of +R media.

Changing the booktype isn't a function of DVDA, it depends on the ability of the burner you are using and usually requires a little utility to tell the burner to change the booktype.

--Scott