Can you put fiberglass insulation on the under side of roof tiles in the loft in the house?
You should not be able to see your roof tiles from inside your house. So no, it can not be done. You can attach insulation to the rafters if that is what you meant.
I would be concerned that this may cause moisture to form between the roofing and the insulation. They make a special foam panel that fit underneath the roofing in between the roof rafters. They allow air to flow from the eave to the roof's ridge.
Not between tiles and roof sheathing, but YES on the inside of the sheathing, between the rafters. However, the recommended location is between the rafters on the FLOOR of the loft, unless you plan on using the loft as a living space.
