Archimedes like mentioned is a good roblox plugin that makes bends easy, here is its forum post it goes into detail Introducing Archimedes 3 - A building plugin?
There are lots of great tutorials on Youtube for blender, maybe not for architecture but im sure there are some, but if you don’t know Blender id suggest learning the basics, and keyboard short cuts etc, as that definitely helps.
I would suggest starting out with basic structures first then gradually experiment with other building techniques, if your kinda new to building, there also is videos on YouTube on build techniques. That said everyone has their oen build style, and ways on building.