• A computer capable of doing teleconferencing.
  So, it will need a webcam with a mic. Most computers have both of these built in.
• Headphones or earbuds. Otherwise, everyone else will hear themselves talk when your mic broadcasts the sound from your speakers.
• Your character sheet. See the "fill out your character sheet" steps for how to get this ready.
  
  If you prefer to make your own character sheet outside of roll20.net, then make sure to still set up a roll20.net account and accept your invitation to our game.

The software can make rolls for you, but if you prefer physical dice they can be found at many game/hobby stores.

In San Francisco, I recommend Gamescape. It's good to support your local shop, because they often hold events to support the local gaming community. For example, you can drop in on Wednesdays to try your hand at D&D.

Or if you prefer, dice can be found at Amazon.

They can be bought as sets, or bought individually. If you buy them individually, then at minimum you'll need one of each of these:
d4, d6, d8, d10 (single digits), d10 (10's digits), d12, d20.

If a roll requires more than one of the same die, you could always just roll that die multiple times. But if you would like to instead roll all the dice simultaneously, then it's worthwhile to get a second d20. (For when you have advantage or disadvantage.)
If you plan on playing a rogue, then it's a good idea to get maybe two more d6's for your "sneak attack" feature.