Getting rid of Arvi or Roy to improve the outlook of the Kings is pointless and horrible decision making if you don't get rid of Kopitar and Doughty as well. As long as they are on the Kings, and want to win another cup, you're gonna have to do what you can to make that happen; and getting rid of Roy and Arvi is not gonna be it.
Are Kopitar and doughty’s contracts up after next season? Is it going to take a significant amount of money to re-sign kopitar and doughty that could hurt signing other players long term? Nope. Completely different situation. No one will touch either of those contracts without a good amount of retention.
Kopitar is still the first line center and it doesn't look like anyone is going to replace him or that he is going to slow down. But if he doesn't want to keep playing here after his contract ends they will probably look to move him too. My guess is he signs for less money and stays in LA on shorter term deals after.
Doughty still has 4 more years after this year on his contract, revisit this in a few years.
Lets say we sign both Roy and Ardvisson. They probably won't want to take short term deals, so if we are lucky we sign them to 4 years. This might be Arvidssons last contract, he may want more years. The cap should also be taking a good jump when the current contracts expire and they might want to go open market and max out what they can get. But lets say about 5-6mil for Arvi, maybe 4-5mil for Roy.
There are already two other Arvidssons in Iafallo and Moore. Moore was just signed and most likely not getting traded. Iafallo still has two more seasons. Then coming up there is still Kaliyev, Fagemo, Andersson and I'm sure I'm forgetting others who are pushing for a spot. The best value we would get for Arvi is now and use it to fill in other spots on the roster and free up cap space.
Roy would be re-signed in a second, if he was left handed. Two RHD probably need to be moved this off season. As much as I would like to keep Roy he has the most value to trade, second would be Durzi. Durzi can play (poorly) on both sides which makes him a more valuable as the team is thin on LHD. Walker needs to get traded too. With Spence and Clarke both fighting for spots next season, I see them rotating on the third pair until one really takes the spot and runs with it, someone needs to go. Roy is a very valuable trade piece and could return a VERY solid piece either at forward or LHD. LA simply has to many RHD.
TLDR: Use them both to possibly upgrade when they are most valuable, or replace with entry level deals to save money and spend elsewhere. Still need to sign a goalie.