You'll probably end up splitting this question into file-services component — which is something that the folks around here might be more familiar with and might be able to help with — and the particular requirements and limitations of the particular (I presume?) raster image printing software that's running on the Microsoft Windows system, the latter of which would be best addressed to the vendor of that package, or with a Microsoft forum.
As a starting point, please post the identity of the RIP package and its version, the Microsoft Windows version, and a few of the error message(s) or diagnostics that you're receiving in the logs, and if and how the file shares are configured on OS X.
It'd be typical to configure SMB/CIFS file-services storage services on the OS X system — both OS X client and OS X Server can share via this Microsoft protocol — and then connect the share via Microsoft Windows and its Windows Explorer tool; the Windows version of the OS X Finder tool. Windows will probably need its security settings downgraded to operate with the Samba SMB/CIFS server found on 10.6.8, or with the Apple Windows File Services found on 10.7 and later. This configuration via the Server Admin.app tool on 10.6.8.
Services from the OS X Server to the Windows box will probably be limited by the speed of the network connection; unless the particular Drobo is unusually slow, I wouldn't expect OS X or OS X Server or the Drobo to show notable differences in file services performance. The network will be the performance bottleneck.
As it's a fairly common omission when working with OS X Server (or most other servers, these days), you will very likely need DNS services working either on or for the OS X Server system, and you cannot reference ISP or off-network DNS servers here; when you're running a server or authentication on a NAT'd network.
To verify local DNS on the OS X Server box, launch Terminal.app from Applications > Utilities folder and issue the following command:
sudo changeip -checkhostname
Entry of an administrative password will be required for the sudo command. You'll get back a message that DNS is valid and no changes are required, or an indication there are DNS or network errors and a reconfiguration is needed.
FWIW, OS X Server 10.6.8 is very old. 10.8.4 is current, and 10.9 Mavericks has been discussed by Apple. I'd suggest using a newer version. 10.8 is current, 10.7 has support and is seeing updates, and 10.6 largely doesn't. When 10.9 arrives, 10.7 will probably fall off of support, if past practices and tradition are any guide.
