Separate the red, fleshy flower part of the rosellas (calyces) from the seed pods.
Wash seeds in water and then place in a saucepan. Cover with water (just) then bring to the boil and boil, covered, for 30 minutes.
Strain and retain liquid but discard seed pods.
Wash the calyces in water and place in a saucepan. Add the liquid from seeds and a little extra water if necessary to cover the calyces (just).
Bring to the boil and then simmer on medium heat for 20 minutes or until fruit is tender.
Remove from heat and measure the volume of the fruit mixture. Add the same volume of sugar and heat gently to dissolve the sugar.
Bring to the boil and then simmer for 20-30 minutes. The mixture will thicken and turn a very bright red colour. Stir a couple of times throughout the process to gauge whether it's thickening and make sure it's not sticking to the bottom of the saucepan.
Pour mixture into sterilised jars and place in fridge once they reach room temperature.