places.sqlite is not about location information, it's about Firefox history and bookmarks.
The file "places.sqlite" stores the annotations, bookmarks, favorite icons, input history, keywords, and browsing history (a record of visited pages).
There is no simple way to move only your
places.sqlite to another location. The following bug report is about setting the
places.sqlite location and it is resolved as WONTFIX. Maybe you can get some useful information from that bug's comments.
You can try taking the whole Firefox profile out of your roaming profile location. See Changing Firefox profile folder location.
Though, this will take out the point from a roaming profile, right? ;)
You can also tell Firefox not to save your browsing history, this can decrease the places file size. Or, Firefox also have an option to delete your history upon closing the browser, this will still let you have history of the current session. (Update: see first comment by Paul D. Waite about this option)