Question about Stanford Torus

Welds are commonly used on large pressure vessels with
high pressures.

You cannot roll a sphere. The standard way to make a
spherical pressure vessel is to cast two hemispheres and
weld them together.

Cylindrical pressure vessels need hemispherical ends
which are welded on to the cylindrical core.

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As for the Stanford Torus, I believe the glass roof is
not a pressure carrying structure, it is unsealed and
presumably has vents in it to allow equalization of
pressure between the two sides.

Metallic pressure vessels are a lot easier to develop
than glass ones.