<p>I am a member of all the roles (Browser, Content Manager, My Reports, Publisher, Report Builder). If I login with a Local Administrator account, I can see and use it fine. Any ideas?</p>

The first thing I would check is to make sure that your normal login is mapped to a role with the correct system-level permissions.  The item-level role definitions don't make a difference for the "Report Builder" button.
From the browser-based report manager interface:
Click "site settings"
In the Security section, click "Configure system-level role definitions"
Click the Role that you want to have this ability (e.g. "System Administrator" and "System User" are the default roles, but I believe that you can create your own if you want to).
Make sure that the "Execute Report Definitions" task is checked/selected.  This is the permission that controls whether or not the "Report Builder" button is displayed.
Click "OK" and then return to the "Site Settings" page.
In the Security section, click "Configure site-wide security"
Click "New Role Assignment" and then map your login (or an AD group to which your login belongs might be even better) to the system-level role you edited in the previous steps.
The forms are pretty straightforward, and I'd guess that your login just isn't mapped to the proper system-level role since you can see the button with the local administrator login.  If that doesn't work, you might check your IIS security settings for the report service to make sure that they're configured to use windows authentication (assuming that's what you're using in the first place).