How can I deploy Windows 8 Pro over WDS so that it is already connected to my domain?
After you read the documentation that I linked to in the comments, you should have an unattended file linked to your WDS install image. The
<UnattendedJoin> section of that answer file is where you can input credentials that are used to join the client to the domain as part of the imaging process.
Are there any blog posts that step-by-step this?
Sure, the WDS docs on TechNet (the official source for Microsoft documentation) covers this very thoroughly. And the WAIK documentation covers advanced configurations.
Any additional roles I need to install on my server (I have WDS, AD DS, DNS)?
If you plan on PXE booting, you need a DHCP server somewhere, but not necessarily on the WDS server. Your WDS server also doesn't have to be a DC. In fact, I'd separate those two roles if at all possible.
Any additional tools that need to be downloaded/installed on the server?
No, but WAIK and WSIM (part of WAIK) are commonly used on a client machine to customize the unattend file and install images. You can install this on the server if you want, but I never bother.