The trouble with thinking of a random number, is that it is a contradiction in terms, and cannot be done.

And what happens if the "random" number I just thought of is 753? Do I reduce it, add the elements, add the first two figures and divide the result by the third, add the end figures and divide the middle, those two options give me 4 and 2 as results, so should I consider 21 (between them on the wheel) as being the first random number?

How many times do I have to wrack my brain?

Here's an easier method.

This is a string of absolutely random numbers within the scope of roulette.

23, 34, 25, 27, 31, 5, 23, 10, 19, 8, 28, 8 and 15.

From the only relevant RNG, the wheel itself.