If you play on mobile and want to do the roll then go to settings left or right multi tap and chose alt attack 2 !!!
NOW FOR THE MAIN PART--- THESE THINGS CAN KILL GIGAS the normal roll does decent damage but if you roll and attack a dino while watching the dino through spyglass you can deal tons of damage (this works in mobile idk about other platforms) i killed tons of rexes,brontos,allos..etc. using this trick
How to do barrel roll on mobile: Go to settings and then go to controls then either go to left multi tap or right multi tap. Then select Reload/Alt attack2. When you are done, go and press on your screen twice on either left or ritght side. And you pteranodon can now do a barrel roll! Disclaimer:wastes stamina alot so be careful. Like so newbies see this!
Not recommended against gigas. The spyglass barrel roll strategy (more info in the popular tips that were a great help to me btw) works well but with one fatal flaw: It's a TWO-WAY damage amplifier. Meaning the giga's attack, If it lands on you, deals much more damage than normal as well. Meaning one hit on a 1500 health ptera with journeyman saddle left my ptera with less than 500 health. So, yeah. Too much risk involved. Good for rexes and maybe alphas but not gigas. I would advise combing the allos strategy with the ptera roll. Let the allos bleed the gigs down first before going for the kill with the ptera. Also compensates for the annoying fact that if the giga dies to allo bleeding it might not give xp. Needs testing but i think it'll work.
Upgrade their stamina and weight a LOT. This flyer is worth it, upgrade his health and melee dmg enough and it can take out raptors on its own (my lvl24 pteranodon killed a lvl20 raptor and succeeded with half of his HP). These lovely birds are easily encumbered by the weight you're carrying so it's preferent if you use lighter armor and leave a few items in the storage so that it's not slow.