gluten free hot cross buns
Hot cross buns are a yeast bread, and without developed gluten most of the air produced by the yeast will escape from the dough. Without developed gluten you won't get the same lift, and your texture will be much more crumbly. 

The typical solution to this is to add xanthan or guar gum to your dough, this will act as a gluten substitute and help trap air and improve texture. Both are readily available in many countries. You can also add both at the same time. 

Suggested amounts for bread are:
Xanthan Gum - 1-2tsp per US cup of flour (about 125g depending on the type of flour)
Guar Gum - 1 1/2 tsp - 1tbsp per US cup

It depends on how stretchy you want your dough to be. Hot cross buns tends to be pretty stretchy, so if it were me I'd add 1 1/2 - 1 3/4 tsp per cup of flour and see how you go. Let us know how it goes!