The veteran star, who played meddling neighbour Karen MCCluskey on the Tv drama, lost her battle with lung cancer aged 72.
Her death came just a month after the hit series finished filming in May (12), and Longoria admits the news was a shock for the whole cast.
She tells Britain's The Sun, "She was an amazing actress and an even better human being. She was an activist and cared about a lot of issues. The last day of filming, she was great, in high spirits and laughing.
"She didn't seem near the end, so it was quite a surprise for all of us that she passed away. We will miss her terribly."
Joosten's character lost her lung cancer battle in the show's finale.