The advantage with external filters is that they can be customised. Apart from sponges and maybe biomedia you don't actually need any other type of media.
Ammonia removing media are not advised as they adsorb ammonia and prevent the bacteria colonies from growing as big as they should. Fine for emergency use, but not full time.
Carbon isn't needed full time either, but is useful for removing medication after treatment has finished of tou ever have sick fish. Carbon might be granules or black sponges. Keep them in the cupboard.
The nitrate pads may or may not work. Many types don't.
Unless there's high phosphate in tap water, phosphate pads aren't needed either.
Is this the filter you have
https://fluvalaquatics.com/uk/product/307-performance-canister-filter-up-to-70-us-gal-330-l/
Some sites say the Roma 240 comes with a 305, others say it comes with a 307. The 305 manual says what should go in each basket, but the 307's doesn't which is why I suspect you have a 307.
In the link is a photo showing what's included with the filter. This is from the website
The long white pads and the blue sponge are the mechanical media, and will also be a biomedium. They go vertically at the side.
The smooth-sided cyclindrical white noodles are biomax, part of the biomedia. These go in the upper baskets.
White cyclinders with angular sides are prefilter, you don't really need those as well as the long side pads.
The lumpy black sponges go in the bottom basket.
The bag containing little black bits is carbon. Leave it in the cupboard.
If you have a bag with little white bits or a bag with little black and white bits, throw them away. The white bits are zeolite, and it could be mixed in with carbon (the mixed black and white bits).
The small white pads are "quick-clear" pads - I would leave those in the cupboard as well.
So:
At the side, the long white and long blue with the blue on the outside edge like this (image from the link above)
Bottom basket - the lumpy black sponges with the lumpy side pointing downwards (also from link above)
And in the top two baskets, the smooth round sided white noodles.
I would not use any of the other media. If you wish, you could buy some filter wool from a roll and cut it down to fit the top baskets snuggly with no gaps round the edges. And place that on top of the noddles.
Ignore anything they say about replacing the media. Sponges and noddles just need washing in old water taken out a a water chnage. If you use filter wool, that will need replacing when it goes into holes - it doesn't wash well, but a length off a roll is not expensive.
