I wish I had an answer, but we're kind of going through the same thing and have taken similar measures (her room has a few books in it, but that's it.) Savannah can play for an hour or two with her blankets on her bed, singing to herself, etc. . . She's missed her nap on many occasions in the last 3 weeks and when she does go to sleep, its always at least 45 min. later, often more like 2 hours, so even if I get her down at 1 p.m., she ends up napping from about 3 to 4:30 (the latest I let her sleep). Nights are then pushed back a little, and she still usually plays, even when she's yawning like crazy when we put her to bed. At least at night I don't worry about her not falling asleep since she does eventually, often faster than at naptime.
The only good thing is that she's been sleeping in later many mornings too--instead of 8/8:30-6:30/7:00, she's sleeping more like 9:30-8:00 some mornings. But not always and she's been way overtired many days--we've had so much more whining and crying lately. Of course, a lot of this might also be because we moved a month ago.
Anyway, I'd just keep up with it. I don't know if you've tried not going in--we don't always depending on the noises coming from her room, we just let her be and she seems to fall asleep as fast or faster when we do it that way. If nothing else, it might help you not get so frustrated--I know how annoyed I get when I'm actually in the room with her trying to get her to lay down. At least if I leave I can go do something else.
~Kim