you can use the piano roll if you like but there's nothing wrong with using the step sequencer in the picture you provided. Naturally when you put your hats on each 16 steps of the sequencer they will be hard quantised basically. this is no good as it creates that sterile no life feel. You have to make slight variations to most of the samples to give it a more human feel. In the top right of the pic you provided you see 2 squares. select the square on the left and find the 'shift' edit mode. manually move notes around and adjust their timing. find the velocity edit mode and make slight adjustments there as well. find the 'pitch' edit mode and make slight changes there as well if you like. Things like that will make your 1/16 notes more interesting.
You can do all this in the piano roll editor. There's an option to turn off the grid edit pattern and just manually paste notes in there and still make the other changes as well (velocity, pitch) if you like. Remember that notes slightly before the kick drum will give more push to a groove and notes slightly after a kick will give a more relaxed feel. It takes a while to work it out but it's worth it.
Another thing you can do is sample a loop at the start of a track that you like. load it into the fl studio slicer plugin. Let the slicer chop up the samples. The samples should now be all chopped up and notes showing in the piano roll. Take a real good look at where all the notes are starting and you will notice that there not all on the 1/16 grid. You should be able to then copy this note pattern and use it as a template for your own tracks with your own sounds if that makes sense. These are just one of many ideas of course.