Stretching and foam rolling will do exactly ZERO for cortisol levels (they might even increase it).
If nutrition and sleep were all that was needed to counteract elevated cortisol from training then nobody who lifts seriously have any issue (since all lifters tend to eat enough and get decent sleep)
Curcumin and fish oil are great for inflammation but wont do much for cortisol.
The best thing you can use to lower cortisol are...
1) high carbs pre-workout (PLAZMA for example). Having carbs in he blood when you train decreases the need to mobilize stored glycogen. And since cortisol is what mobilized glycogen it means less cortisol release
2) Glycine POST workout (5-10g) and at night can also help
3) Phosphatidylserine at 800mg post-training lowers cortisol too
4) Vitmaine C post workout and at night will also have a positive effect