Frair Laurence is held responsible for the deaths of both of them because Romeo drank the poison because he thought Juliet was dead and when Juliet woke up, she saw that Romeo was dead so she stabbed herself with Romeo’s dagger.
Even though, Frair gave Juliet a fake potion at least he didn’t give Juliet a real one that would make her die. Also, he listened to what Romeo and Juliet wanted unlike their parents. Frair married them because that’s what they wanted and he also wanted to stop the feud between the Capulets and the Montagues.
To conclude, Frair Laurence is overaly responsible for the deaths of Romeo and Juliet. He married them secretly, gave Juliet a potion and a plan to run away with Romeo, and lastly did not give Romeo the information about the plan. Frair Laurence should be put away or banished until his death