It depends entirely on their goals for a trade. Not to say Robertson is high on their list but to get a top prospect like Minten seems a stretch as well. I'd put Frost's value in the same ballpark as Liljegren -- a former 1st round pick with interesting skillset and potential that has struggled to consistently put it together and now is sitting out games while healthy.
Fair point... but I feel like there's a bit of a difference in the Liljegren vs. Frost discussion, in that the Flyers don't need to trade Frost; whereas the Leafs needed to trade Liljegren with all the guys on LTIR.
The Flyers don't have any roster or cap issues that I'm aware of. While they have healthy scratched Frost, I think that's more of a "John Tortorella" thing just like he scratched Sean Coutourier last year, and he's likely to be back in the lineup their next game. Liljegren, had fully lost his spot.
I think it's also "easier" for an acquiring team, just by virtue of the fact that he's a centre (and there are 12 forward spots vs 6 D), to think to themselves, "he may be my #2 or #3 centre, but if that doesn't work out, I can get use out of him on the wing".... whereas Liljegren, has a much more "specific" fit.
It's somewhat unfortunate that there couldn't have been a deal done around Frost for Liljegren; as I think that's a much easier deal to justify for Philly, versus "let's dump Frost for a collection of picks". Teams don't dump players for picks unless they have to, or are already writing themselves off. Philly's not going to write themselves off ~15 games into the season.