Why would he make a Ring knowing that the One, were it to re-surface, would be its master?

Perhaps he thought that the one was lost forever?
Perhaps, in his studies, he discovered how to forge Rings of Power which would not be subject to the One?
Perhaps, as had been suggested before, the One Ring only controlled the Rings which were already in existence when it was forged and Saruman, knowing this, had no fears that his Ring would be ruled by the One?

I favour the last option. A number of Rings were forged before the One and, indeed, before Sauron had a hand in instructing the Ringsmiths. I think (and it's just my opinion) that Sauron forged his Ring specifically to control the main Rings of Power that he had been involved in making. He could 'read the minds' of the wielders of the Three (and vice-versa, according to Galadriel) but not control them. Saruman must have known about this and therefore was not worried about being controlled.

However I don't know why Saruman's mind wasn't laid open to Sauron as soon as he began to use the Ring. Or perhaps it was, and that, along with the use of the Palantir was how Sauron overcame him.

Sorry for rambling.