I am not sure that I understand what you are asking. The manifest file is used by Runtime to compare the local copy of the solution to the one being loaded. You don't trigger runtime by using the manifest file.

If you are starting Runtime from a bat file using the command; OpenSpan.Runtime.exe project="\\Path\to\wherever\the\project\is\located\MyProject.OpenSpan" and you want to supply an additional argument to Runtime that you can read in the solution, then you can do that. In the attached solution, I have a script you can use to read the command line of a process. From that string, you can extract whatever you pass into it. In my case I used the following command line;

OpenSpan.Runtime.exe project="\\Path\to\wherever\the\project\is\located\MyProject.OpenSpan" MyConfigPath="Whatever the path to my config is"

The script will return that entire string which you could parse out to look for only the MyConfigPath part. I am not sure what this would look like if Runtime were triggered from Robot Manager, but I assume it would be similar. In that case though, you are probably using the synchronization engine launcher which goes away before Runtime, so you might not be able to read anything from there. Another option is to simply write whatever value you want to a text file and then read that text file from within Runtime (and then delete it).