So I've finished my first Witcher 3 playthrough, which started from my first Witcher 2 imported save (where I did Roche's path). Roche welcomed me and treated me like an old time friend, we played Gwent, and he even agreed to come with Ves to help me at Kaer Morhem. Finally we fought together against Radovid's guys and Dijkstra so it kinda ended in bromance LOL.

Now for a future playthrough I was thinking about using my Witcher 2 Iorveth's path save, but I've read that neither Iorveth nor Saskia appear in this game so, would it be pointless? I mean, is there any benefit in playing The Witcher 3 with an imported Iorveth's path save? Is there any negative consequence regarding quests involving Roche's in this game?

No and no.

crap. I am starting my first witcher 3 playthrough just now and I just finished w1 and w2 always siding with the scoi'atel (I mean who'd want to cooperate with the nazis ;P ) ... oh well no candy for that in w3? To think I even let Triss rot in her cell just so saskia could make the dream of a great multiracial stronghold at vergen come true, and now witcher 3 doesn't even follow up to that?

You lose.

hehe, true :)

Nazi's? really? Your vocabulary is truly that shallow? If anything the squirrels are the least sympathetic of the bunch. Much like certain groups in 2017, they constantly moan and demand special treatment for past crimes against their long gone ancestors whilst acting like very heartless animals.

The human racists aren't great either but it is hard to blame them for their intolerance with the way the elves behave. Ironically, their multicultural city falls after the second game and their leader killed. Sounds like certain modern events in the making haha.

well, I should have written racists which is just what the order is.
as for the multicultural city (vergen) in witcher two, I beg to differ it stands strong with a living unleashed saskia as their leader at the end of my playthrough.
As for real life politics, I won't even comment.