Låtsattack säger (PHB s.96):
You don't need advantage on the attack roll if another enemy of the target is within 5 feet of it, that enemy isn't incapacitated, and you don't have disadvantage on the attack roll. So, as described you cannot sneak attack.
Men fördel och nackdel säger (PHB s.173):
If circumstances cause a roll to have both advantage and disadvantage, you are considered to have neither of them, and you roll one d20. This is true even if multiple circumstances impose disadvantage and only one grants advantage or vice versa. In such a situation, you have neither advantage nor disadvantage.
Så om rogue hade fördelen att avbryta nackdelen (säg att vara dold) och hade en allierad närliggande fienden (eftersom nackdelen negerar fördelen och vice versa) kan de smyga anfall .