A glass roof brings light in, no argument there. What needs discussing is what happens in summer. Sun from directly overhead is far stronger than sun from the side, and without heat-control glass the space underneath becomes unusable by mid-afternoon.
So we treat low-e heat-control glass as standard rather than offering it as an option. On safety, the upper pane should be toughened and the lower one laminated. Laminated glass does not fall through even when it breaks; the interlayer holds it. On glass sitting above your head there is nothing to negotiate.
An opening rooflight ventilates and lets hot air out at the top. Add the rain sensor. A vent left open while you are away will soak the room in one downpour, and the sensor costs little next to the motor.
Watertightness is the critical detail here. Water rarely comes through the glass; it comes through the joint between glass and frame, and through the valleys. The aluminium frame needs drainage channels so any water that gets in is carried back out. A skylight built without them will drip sooner or later.
We build rooflights and glass roofs for atriums, stairwells, terraces and winter-garden ceilings. Prices depend on size, glass type and whether it opens. If it is being planned together with a pergola or winter garden, we do a single survey for the lot, at no charge.