no fuckin clue what a twamp is but if you roll .2 joints you'll get 5, roll .3 you'll get 3 and have .1 left over, I usually smoke .5-.7g joints so for me i'd usually get 1-2 from a g, hope i helped in some way
after looking on urbandictionary i found a twamp to be a 20 sack that has 1g....so..youd beable to roll like 2 joints...maybe more