Imam Ibn Baaz was asked about the one whom raises his head in Sujood before the Imam.
If you raised your head before the Imam, then it is upon you to return into Sujood, then you raise your head after him. If you didn’t do that [return to Sujood and wait till he raises his head] out of ignorance, then there is nothing upon you and the prayer is correct. As for if you knew the legislative ruling and you did this purposely and didn’t return to Sujood, then your prayer is null and you must redo it. As for if you were ignorant, then your prayer is correct and you should refrain from doing this [raising the head before the Imam]. If you raised your head thinking the Imam raised [his head], then you became aware that he hadn’t raised [his head] yet, return to Sujood and then raise after him.
Majid Jawed Al-Afghanee