The roulette wheel itself is a marvelous little piece of work. A lot of
care is put into the manufacturing process, as it has to be completely
free of biases. Online roulette wheels of course are simply random number
generators, no need for good engineering there, just good programming.
Roulette rules don't allow for late bets, as a team of players could position
somebody with a sharp eye at the right angle from the wheel, guess the
falling number just as the marble comes down, and give hand signals to
someone close to the table who could put money down on the likely number.
Artists have perfected these scams, since an inside bet in roulette rules
pays off at a nice high ratio. And if these people have perfected something
as complex as predicting the landing number by seeing the wheel a little
after bets are called off, then you know a biased wheel could certainly
be taken advantage of. A biased wheel is one where the engineering precision
has been compromised to some degree, which can be caused by any number
of variables, from human tampering to natural wear and tear. If a wheel
develops an anomaly in the way it spins, it can turn out that one number
or a set of numbers near one another on the wheel get the marble more
often than chance would regularly allow for. If you are aware of the imperfection,
you could make a killing. Sadly, people have, and so now the casinos check
their roulette wheel on almost a daily basis for inaccuracies.

So we can't readily take advantage of the roulette wheel, but that doesn't mean we shouldn't take a closer look at it. Taking a look at the layout of numbers reveals many a pattern. The numbers have been spread around the wheel in such a manner that things are as even as possible. Every odd number on the board is directly across from the next highest even number. Standard roulette rules dictate that pairs of even numbers alternate around the wheel with pairs of odd numbers. In fact, a balance between red and black, odd and even and high and low has been achieved to some degree with the engineering of a modern roulette wheel. Roulette rules relate directly to the table layout. Many people as me, if what you say is true and every spin on the wheel is independent of the preceding one, then why is there any point to adding order to the placement of numbers? Good question, simple answer though. You can bet on as many numbers as you want, and more than that you can bet on numbers and ranges (high/low/columns) at the same time. If there were a concentration on any one area of the wheel of, say, odd or even numbers, the casino could not accept bets on sets of these numbers, because the odds on one set would not be the same as the odds on another set.