If say the enemies roll 12, 15, and 19 in stealth, and the players roll 11, 14, 17, and 20 in perception, does everyone but 11 go in numerical order, or how does that work?
EA = 12 stealth
EB = 15 stealth
EC = 19 stealth
PA = 11 perception
PB = 14 perception
PC = 17 perception
PD = 20 perception.
PD sees EA, EB, EC
PC sees EA, EB
PB sees EA
PA doesn't see anyone
PA is surprised and can't go during the surprise round
PB can only deal with EA during the surprise round
PC can only deal with EA and EB during the surprise round
PD is not surprised and can deal with any of the enemies on his initiative round.
Everyone still needs to roll initiative to know what order they go in.
Let's pretend there is another Enemy (EZ) who's stealth is 22, who chooses not to go in the surprise round. When they finally do decide to go, thus revealing themselves, who can react to them? Is it a mini surprise round, and players can only take a standard action against EZ or are they free to take full actions against EZ if they go after him?
Technically, they get a full round against EZ. No special allowances are made for combatants who reveal themselves in the middle of an ongoing fight. EZ gets treated the same as if they had revealed themselves in the surprise round
However, the initiative rules are silent on how to add new combatants to a fight, so its a bit of an edge case when you throw mid-combat stealth and opponent unawareness into the mix.
Once the surprise round is over, it's over.
No one can see EZ until she reveals herself.
Once she reveals herself, she's fair game for everyone follows her in initiative order.
ETA
I'd have EZ roll initiative along with everyone else. She gets to act on her own initiative roll, and once she reveals herself, she's in rotation just like everyone else.
[ignoring all the rules about readied actions, which complicate initiative order]