Is a roof made out of glass viable?
You lose more heat through ceilings than through other surfaces (because the warm air is touching it, and because of good convection currents). 

The insulation value of glass is very low. To put it in USA terms, a single pane of glass is R-1, while many house walls are R-20 and ceilings R-30. I've seen superinsulated roofs at R-60. Even triple-pane glass is only R-3; inert gases inside help, but over time they leak; you probably can't have a good seal if you want to run a curtain through them.

During the day, insolation will warm your house through the ceiling (probably too much, even in your part of the world), but at night when you're only losing heat, you'll really feel it. You'll use a lot of energy to stay warm.

At the same time, it would be very expensive. Windows are generally an expensive feature in a house. Sloped windows should be tempered for safety, which makes them even more expensive. And you're talking about a huge area.

Roofs in particular get beat up pretty hard; standard roofs (asphalt shingles) around here last about 20 years. 

Meanwhile, you lose the opportunity to put photo-voltaic panels on your roof.

However, you can get a lot of what you're looking for with a much less ambitious approach.


Small solar tubes bring in a huge amount of light for their size.
A skylight over your bed can let you stargaze in comfort. Put your bed up high for a wide viewing angle.
Spend more time outdoors.