Howie Rose, the Islanders’ television broadcaster for 20 years, is done with the Nassau Coliseum, having called his last game there. But Rose is not done being “angry’’ that Saturday’s first-round Game 6 against the Capitals may be the last Islanders game ever on Long Island.

If the Islanders, trailing 3-2, don’t win the series, their next home game won’t be until next fall in Brooklyn. Because NBC is televising Saturday’s game, Rose won’t be calling the contest for MSG-Plus.

Rose could be back for Game 7 in Washington, but the national networks take over for the second round. Tuesday’s Game 4 marked Rose’s Coliseum swan song. MSG-Plus ratings were up 50 percent for Isles playoff games from 2013’s number.

“My emotions aren’t as much melancholy as anger,’’ Rose told The Post Friday. “It never should’ve come to this. So I’m not looking at it through the mechanism of, ‘Gee, wasn’t it great, hearing all the noise in the building this season?’

“All that stuff, I just get angry, I’m pissed off they’re leaving,’’ added Rose, a Nassau County resident. “I’m not happy about it in the least. I’m not yet in the process of trying to make sense of it in a historical standpoint that creates wistfulness. My blood boils thinking about them leaving. Sorry if I don’t have any flowery prose.’’

Then Rose uttered what many torn Long Islanders will feel when they walk into the house off Hempstead Turnpike for the game Saturday at 3 p.m. when the Islanders try to keep the series — and building — alive.

“The Islanders should’ve been on Long Island for freaking forever,’’ Rose said.

Redevelopment of the Coliseum turned into a political mess, so after 43 years, they are leaving for the borough in which Rose was born. Rose, who grew up a Rangers fan and used to call Blueshirts games on radio, said the Islanders became “a political pawn.’’ That, he says, hurt attendance because of stalled plans to transform the decaying arena.

“You look at the low attendance figures in the past, the fans just were beaten to a pulp by ownership issues, management issues, every possible series of events,’’ Rose said.

“A confluence of circumstances that discouraged people from showing up. The place was a dump. No one took any lengths to make it anything other than a dump. It never should’ve come to this. Everyone was trying to see what they were going to grab from it.’’

Rose, who has a contract to continue calling games at Brooklyn’s Barclays Center, said his feelings in no way suggest he doesn’t think or hope it can work in Kings County:

“This has nothing to do with Brooklyn – I hope they have eternal success there.’’

But he’s still stunned the Islanders couldn’t make it work on Long Island, like the Nets couldn’t make it work back when they won titles in the ABA. The Coliseum will be renovated into a smaller venue — partly to attract minor league sports.

“Two major league teams were here — now the idea is to downsize it,’’ said Rose, who is calling the Subway Series Mets-Yankees games for 710 WOR AM this weekend. “Long Island is actively trying to be a minor league town when it was major league. Good luck to Nassau County.’’