Early into Palace's FA Cup win against Millwall, Roberts and Mateta collided, leaving the French striker being rushed to hospital and having 25 stitches placed to treat a head wound.
Roberts was sent-off for his actions and has been heavily criticised by pundits and Palace officials since.
But Mateta told Sky Sports: "Liam texted me while I was in hospital and I told him 'it is OK, it is football'. He apologised. He was worried.
"I don't think he woke up and thought 'I want to cut the head off JP.
There is a lot of pressure. He wanted to do good, too much emotion makes you do crazy things. It was just a mistake. You learn from it."
Roberts has been banned for six games for the clash.
Mateta hopes to be clear to face Fulham in Palace's FA Cup quarterfinal.
Asked about a return, the striker added: "I don't know. I'm still in touch with the specialists and the doctor. Hopefully soon. Hopefully I can play (against Fulham)."