borta actually sounds pretty good here. The present TTS isn't that good with r sounds generally, but here I think it sounds very natural. Compare with native speakers here: http://sv.forvo.com/search-sv/borta/
In Standard Swedish and most dialects, R melts together with consonants D, T, N, L and S to form what is sometimes called retroflex consonants (aka supradentals or postalveolars).
English Wikipedia has good articles on those, follow the links from the table here
This one is about RT: https://en.wikipedia.org/wiki/Voiceless_retroflex_stop