I got a pack of these cable tie mounts off eBay a while ago. They were about $9 for 100 pieces including postage if you look around.
Buy the black ones if at all possible as they should stand up to the sun much better than the white version.
There are a couple of different sizes. These ones are the smaller type and fit in the mortar area of brick walls.
I used a small self tapping screw (6 or 7 gauge?) to attach them to wood. You’ll need to use a wall plug for brick or concrete of course.
These mounts proved useful for securing lightweight motifs to brickwork and loose wiring up beside my fence gates.
Some people have also used this type for securing light strings to their roof.
The adhesive backing they come with is pretty useless, so peel and clean the adhesive off and silicone them to your tile or iron roof instead.
A heat gun can be useful to soften the adhesive backing making it easier to remove.
Whether or not you use the original backing, you must clean the surface you want to stick them on first.