Re: '08 roadster will not start
SOunds like the battery is low - so it wont' engage the starter.
And when connected to a strong battery - it is doing the "three and nothing", sign of a blown SKREEM.
If you changed the SKREEM and got it to start, you may find that the battery is also bad, or there is a current drain with the car off -but that's minor compared to a blown SKREEM.