What does it mean in other words?
who was last seen round-housing Vietnamese extras in B-movies in the ’80s, back when he was only pushing 50

the context:

Meanwhile, the NRA has…Chuck Norris, doing its “Trigger The Vote” Campaign. An actor, in the sense that he showed up in films, who was last seen round-housing Vietnamese extras in B-movies in the ’80s, back when he was only pushing 50

Question

What does it mean in other words?
who was last seen round-housing Vietnamese extras in B-movies in the ’80s, back when he was only pushing 50

the context:

Meanwhile, the NRA has…Chuck Norris, doing its “Trigger The Vote” Campaign. An actor, in the sense that he showed up in films, who was last seen round-housing Vietnamese extras in B-movies in the ’80s, back when he was only pushing 50

Answer

"Round-housing" refers to a round house kick, a type of kick in martial arts.
"Vietnamese" are people from Vietnam.
"Extras" are people in movies who have little or no lines and are not important to the story. In martial arts films, they are usually bad guys who are attacked and quickly killed or subdued.
"B-movies" are low-budget movies.
"80s" are the 1980s.
"Pushing 50" means getting close to the age of 50-years old.
So it means:
"who was last seen kicking people in low budget movies in the 1980s, when he was almost 50."