To begin, friar Laurence is responsible for Romeo and Juliet’s death because he formulated the dangerous plan that ultimately led to their tragic demise.

For example, in the play Romeo and Juliet Laurence suggests to Juliet that she take a potion that will make her appear dead in order to avoid marrying Paris.(Act ?. Scene ?. Lines ? -- ?)
what act and scene and line?

In Romeo and Juliet, Act 4, Scene 1, Lines 68-118. This is when Friar Laurence gives Juliet the potion plan.