Gas bottle safe in direct sun?

It's a sensible and understandable question.

However, there's no need to do anything about it. Repsol and Cepsa bottles are designed to withstand many times the actual pressure of the gas inside them, even when this is heated. When they get empty bottles in for re-filling, they select a percentage for destructive testing - I can't now remember the details, but remember thinking 'wow' when I read what pressure they have to get to before they explode.

Enjoy your roof terrace - no need to keep sneaking glances at your gas bottle!

Phew that's put my mind at rest, weren't glances...more scrunched up winces!!  ....now I'll relax lol. 

If you still feel a bit apprehensive, why not purchase a suitable sized storage unit from Leroy Merlin, or similar outlets and keep your bottles in that, You can get them with air vents in to allow air circulation and will keep the direct sunlight off your bottles.

You mention RED gas bottle, which indicates containing propane gas, they are perfectly safe for outdoor use both in hot and cold temperatures. On the other hand Butane bottles coloured blue are only approved for indoor / sheltered use as Butane is only approved for a specific temperature range. Worth a check with your supplier for peace of mind.

The reason for the above approvals is that if you've got a butane bottle outside, and the temperature gets down near freezing, then the butane doesn't vaporise well, so your water heater or barbecue etc may not fire up properly.

This can be aggravated as the liquid gas turns into vapour, because this causes further cooling.

By all means put your bottle bank in an enclosure, for aesthetic reasons, but make sure the enclosure is ventilated.

As an aside, remember to check the expiry date on the red plastic gas pipe, and change it when necessary. You can buy the piping at any chino or ferreteria, and the cost is minimal.