Assumptions made: Talonflame has 252 Attack EVs, and 0 HP EVs. This means it should have 153 HP.
Now,
Brave Bird gives 1/3rd of the damage it has dealt as recoil. Rough Skin gives 1/8th of a foe's total HP as recoil and Rocky helmet 1/6th. All these are calculated individually and summed up in the end.
Here are the calcs and the recoils:
Talonflame with Life Orb.
>252+ Atk Life Orb Talonflame Brave Bird vs. 232 HP / 252+ Def Garchomp: 79-95 (37.2 - 44.8%) -- guaranteed 3HKO
Recoil:
BB: 26-31 HP
Rough Skin: 19 HP
Rocky Helmet: 25 HP
Total: 70-75 HP
Talonflame with a crit.
>252+ Atk Talonflame Brave Bird vs. 232 HP / 252+ Def Garchomp on a critical hit: 93-109 (43.8 - 51.4%) -- 7.4% chance to 2HKO
Recoil:
BB: 31-36 HP
Rough Skin: 19 HP
Rocky Helmet: 25 HP
Total: 75-80 HP
Talonflame with no item or crit.
>252+ Atk Talonflame Brave Bird vs. 232 HP / 252+ Def Garchomp: 61-73 (28.7 - 34.4%) -- 5.6% chance to 3HKO
Recoil:
BB: 20-24 HP
Rough Skin: 19 HP
Rocky Helmet: 25 HP
Total: 64-68 HP
Talonflame with a Life Orb and a crit.
>252+ Atk Life Orb Talonflame Brave Bird vs. 232 HP / 252+ Def Garchomp on a critical hit: 121-142 (57 - 66.9%) -- guaranteed 2HKO
Recoil:
BB: 40-47 HP
Rough Skin: 19 HP
Rocky Helmet: 25 HP
Total: 84-91 HP
Hope I helped!