(These instructions pertain to Lion and Mountain Lion, 10.7 & 10.8)
Boot to the Lion recovery partition, you will also need the IP Address of the Drobo, name of the Time Machine Share on the Drobo, the Admin login and password for the Drobo. The IP address can be found in the Drobo Dashboard>Drobo Settings>Network>Network Settings. The Time Machine Share name can be found by looking at the Shares screen in Drobo Dashboard.
Please note, lines beginning with > are lines that you type in terminal.
For more information on Apple's recovery mode please look here: http://support.apple.com/kb/HT4718
Boot the Computer into recovery mode.
Go up to the Utilities menu and choose Terminal.
Once in Terminal:
> cd /Volumes
Create a sub-directory in Volumes as a mount point for your time machine share.
> mkdir TimeMachine2
> cd TimeMachine2
pwd should show /Volumes/TimeMachine2
Mount the network share with your login & password.
> mount -t afp afp://[Admin_name]:[Admin_password]@[Drobo IP Address]/[Share Name] /Volumes/TimeMachine2
> mount -t afp afp://myname:email@example.com/backup /Volumes/TimeMachine2
It may take a minute or two to mount.
> ls -la
Note the EXACT name of the sparsebundle
> hdid /Volumes/TimeMachine2/[first three letters of the sparsebundle name and then hit TAB]
Hitting tab should autocomplete the Time Machine sparsebundle name. It may not look the same as it is displayed above as it escapes spaces and special characters. If it auto completes the name then hit return. If not please contact support.
When this returns to the prompt it has opened the sparsebundle.
Switch back to the main recovery section by quitting the Terminal.
Select Restore from a Time Machine backup and then click Continue.
After the search it will show you the Time Machine Backups directory as a volume that contains your backup. Select that and click Continue.
In the next screen you will see all the backups that you can restore from listed by time and date.
Select the backup that you want to restore.