Would they be circular or would they develop square like as Roman or Greeks
Square.
The neolithic farmers in Europe already lived in longhouses thousands of years before the Romans and Greeks.
With the small side facing the dominant wind direction.
Some pictures of Germanic longhouses
here and
here.
However the size of the longhouses varied between the regions. Some went for really gigantic ones, around 60 meters long. With everything under one roof. While other regions preferred smaller ones. One for the extended family, one for the farm animals, one for storage.
No windows (no glass), only some portholes which could be closed with wooden hatches. Wooden or stone floor in the family rooms.
For building they used the materials easily available. Wood of course, stone when possible (like for the lower walls so that the wooden walls wouldn´t touch the earth.). At the coasts, reed for the roof.
Generally I´d say look at the climate in a region.
In warmer regions (Mediterranean, Middle East) you end up with "white" buildings and many large windows and doors to capture the wind for cooling.
In colder wetter regions the first primitive houses probably will look a lot like those longhouses. Small side to the wind. Roof almost reaching to the ground, small, easily closed "windows". Optimized to withstand heavy rain or snow.
How you then use those origins once they develop an advanced civilization is then up to you.

Simply the invention of glass for windows or iron stoves would change constructions. Or mortar.