Only if it's on the DLS. Right click on the route and click "View Dependencies". Missing dependencies that are on the DLS will appear as stated above, but unknown dependencies (ones NOT on the DLS) will be listed as unknown <KUID:12345:67890>.
If I encounter that I look for the KUID on google, there you might find the place to download it, OR threads about others looking for them which may lead you to a place to download them.