You can booktype DVD+R, DVD+RW and DVD+R DL to DVD-ROM. DVD-R, DVD-RWRW, DVD-R DL and DVD-RAM cannot be booktyped.
Even though you can booktype -R media it's not quite the same as booktyping +R. With +R media there's no booktype on the disc until it's burned. That means 100% of players will see the booktype you burn on it as the correct one. With -R media there's a booktype put on the disc by the manufacturer. When you change the booktype you're adding an additional set of data to the disc, which may or may not cause a player to ignore the original and believe it's a DVD-ROM. In reality, for newer players it shouldn't make any difference anyway.