I think that friar lawrence had to blame for their deaths because he was there through this whole thing with them. he has given them a lot of things through the whole play. He gave juliet the potion so she could fall asleep for 48 hours so she didnt have to marry paris, but what happened was is that before friar sent romeo a letter to meet him at the coffen for juliet.
After that Romeo didnt get the latter. So romeo didnt know what was going on. So when