This is a retarded route to go down
Your basic taxes should cover this. By opening a casino to fund the roads you will just ensure that money from your taxes is no longer allocated to this sort of thing. In the UK we have a national lottery (a tax on people who cannot do maths) and that now funds our arts and sports and a large part of investment in school facilities. This means the government can divert money away from these things to fund pointless wars and investment in new ways to tax us and remove our civil liberties.
Rather than pushing for another form of funding the public in California should push for transport to be put higher on the budgetry agenda.