Don't say roof, Reiner! It's called a Bimini Top no matter how ornate it is. As you have read so far, the greatest preference is for a folding Bimini, and virtually every Chandler carries one or two lines of hinges and bases for
stainless steel tubing between 3/4" and 1 1/4" OD. A simple bender is the fanciest tool required. I have not seen a Bimini that required welding, but I too would buy a TIG just to know how to use it.
Try to design it with a set of simple curves or your canvas bill will choke a goat. Keep the spans down to the width of a bolt of cloth, with seams. In the US, most Bimini's are designed to be left up while sailing, which means you need to accomodate running
rigging like
sheets and travellers, but its not that hard. Some consist of two tops, one in front and the other behind the mainsheet, with a snap on panel between for motoring in the rain.
I have seen some built out of PVC
plumbing pipe, and the visual effect is pure Hick, in case that's what you like. Individual tastes do vary!
In lower lattitudes many liveaboards stretch a sun cover over the cabintop too. They report a ten degree or more temp drop inside as a result. If you don't have a
watermaker, you might try rigging a rain barrel!
Put your
solar panels on a stand-alone frame that stays up when the Bimini is taken down. Make it sturdy enough to crawl on. This part is frequently called a
Radar Arch, Targa Arch, or such. With a good bit of ingenuity, it can also be part of your bimini, giving you a good deal more shaded space. Keep in mind that lighter vessels can't carry a lot of weight aft, so don't get carried away with
dinghy davits,
antenna farms, vane
steering and
diving boards!