1. If the DM outright states the spell. For example, "She lifts her finger and casts disintegrate on you." and if the player has taken the time (research) to know what spell level that and every single spell's level is from memory, I think their character should also know the spell level in game.

2. If the DM doesn't specifically say the spell, perhaps use an intelligence check to see if you can properly identify the spell or not. Again, just what the spell is, not the actual level.

Using a player's rogue memory, without looking it up, while under duress seems in keeping with counterspell.