I'm new to rosies as well and there is a lot of conflicting information out there. Even their taxonomy is a big mess! Rosy boas aren't terribly popular outside the US west coast so it's nice to hear they're getting some attention in Germany.
I think the ideal setup is what is good for the snake and keeper, and fortunately rosies aren't picky.
Rosies are secretive crevice dwellers and like confined spaces, but I like to give my rosies the option to stretch out when night falls and it's time to cruise. So I keep my ~3 year old costal female in a US 20 gallon glass terrarium. My younger and much smaller rosy is kept in a 10 gallon. Rosies shouldn't need anything bigger than US 20 gal. long. Since males are smaller they could be put in a smaller terrarium.
I use a glass terrarium because it works for my situation and it was the easiest route. It was readily available in retail stores here and required hardly any setup. Just make sure the lid is secure.
I do have a plastic "sweater box" too, but I found the traditional glass terrarium easier to keep the humidity low. This of course depends on my environmental conditions. For snakes that require higher humidity a plastic tub or PVC terrarium is often much better than a glass terrarium. The other thing to keep in mind is if you do use a plastic tub that the lid needs to be secured. I have several binder clips on mine but others have come up with other creative ways to keep their snakes from busting loose. (They are strong!) In a rack system often there isn't a lid as the top of the tub runs flush to the shelving of the rack. Using a plastic tub is a cheap option but requires more DIY. I haven't had any experience using a wooden terrarium.
Will a rosy do well in a plastic tub? Yup, just as long as the lid is secure, the temperature gradient and humidity are in good order, and the snake has hides to feel secure in. Snakes don't need anything fancy. They don't care.
How you maintain the climate of your terrarium is based on what the climate of the room you keep your snake is. For example, I'm lazy and cheap. My house has poor insulation and running the central heat to 75-80 F during cold days is expensive for me. So it's set at 70. This is a bit chilly for my rosies and may cause them to stop eating, which I obviously don't want. So in addition to having an under tank heater ("belly heat") to create a hotspot I use a ceramic heat emitter. This hangs above the terrarium and raises the ambient air temperature of the terrarium. Some people raise the temperature of the whole room to achieve the correct ambient temperature, but the ceramic heat emitter saves me several $ overall. Right now since the ambient temperature in my house has been consistently ~80 F I have turned off the ceramic heat emitter.
You will need a thermostat or dimmer (rheostat) to control your heating device(s). Thermostats are more expensive but more reliable. Under tank heaters typically do not have a controlling device to set the temperature and without one they can easily get to 130 F! That is too hot for any snake. I use a rheostat specially sold for reptiles. Again, I'm cheap and I only have two snakes. For the ceramic heat emitter I use a table top light dimmer. With rheostats you have to periodically check the temperature and set the dial accordingly. I highly recommend getting a temperature gun.
The thing to keep in mind if you do decide to go with plastic is FIRE SAFETY. UTHs get hot and shouldn't be in direct contact with plastic. Flexwatt (heat tape) is a better option here. You will have to cut and wire the Flexwatt yourself. Oh and ceramic heat emitters get fiendishly hot as well. Do not touch it when it's on! Make sure you have the correct fixture for a CHE.
Lighting is not necessary. Rosy boas are nocturnal.
Any wood mulch/shavings that are safe for other snakes are safe for rosies. Depends on what's available to you. Sand is controversial. I've read that rosies can do just fine with sand as their sand boa cousins can, but I still hear that it's not preferred. Rosies in the wild don't often inhabit sand anyhow. The closest I've seen to "sand" is actually decomposing granite. (I used to live in their natural habitat -- San Diego and Riverside counties in California.)
I give my rosies 24/7 access to water. If rosies are kept in a
chronically humid climate they may develop respiratory illness. A day or two of humid weather won't kill them nor will a water bowl. If you're having difficulty keeping the humidity from getting too high then limiting access to their water bowl will bring it down. This is not necessary for my rosies as humidity stays between 45-60%. It's dry enough for them to drink as they please.
Hibernation or brumation is not necessary if you do not intend to breed your snake. Pet snakes are happy to be warm year round.
Ultimately it depends on what you want to spend, what's available in your area, how much setup work you want to put into it, what you want aesthetically, how easy the enclosure is to maintain, and of course what's comfortable for the snake.
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