Preheat oven to 210°C/410°F (190°C/370°F fan-forced).
Saute spinach with garlic and olive oil in a large pan until just wilted. About 1 minute.
Remove spinach into a bowl and when cool enough to do so, squeeze out as many liquids as possible with your (clean!) hands. Reserve or discard spinach liquids. (note 3) Roughly chop squeezed spinach.
In a large bowl, combine spinach and ricotta filling and mix until well combined. Taste and adjust for seasoning.
To assemble the rolls, cut each puff pastry sheet with a sharp knife by half, into two long rectangles.
Spread ¼ of the filling onto each rectangle sheet in a log form, lengthways. Brush egg onto the opposite end. Roll up like a large cigar and seal. Repeat for remaining 3.
Cut each rolled pastry into 3 equal pieces, making 12 small rolls. Place onto a lined baking tray, seam side down. Ensure wiggle room between each roll as they will puff up!
Brush each rolls with whisked egg and generously sprinkle with sesame seeds.
Bake on the middle shelf of the oven for 25 minutes or until deep golden.