Overview and images of basalt as a rock type are here: Basalt
Lava roses or more correctly rosettes really do exist. I stumbled upon one when visiting Tenerife. Such formation is a special type of columnar basalt.
When basalt sheet cools slowly it contracts and vertical cracks emerge and propagate through the cooling lava, leaving behind prismatic columns. These columns are quite well-known phenomena of volcanic regions. However, sometimes the cooling lava mass doesn’t have a sheet-like morphology. What if it is a lava tunnel with a spherical cross section? In this case such lava rosettes can form. Bedrock is surrounding hot lava mass and cools it equally from all sides.
Lava rosette in Tenerife. The width of the view is more than 10 meters.