In Montreal, Spaniard Alonso passed the ultra-rare 300 grand prix mark, but next weekend he will tackle Le Mans and for 2019 he is linked with Indycar.
Rosberg, the 2016 world champion, said that almost everybody wishes for more success in Formula 1 for the two-time world champion.
"We all want to see that, but nobody wants him because of his political games within the team," the German is quoted as saying by Sky Italia.
Rosberg said that he is not sure how Alonso can stay motivated to remain in F1 with McLaren.
"I don't know how he does it, I really don't. He knows he's one of the best, but he cannot qualify 14th. It's incredible," the former Mercedes driver said.
Alonso sits seventh in the driver rankings following the Canadian Grand Prix.