Like DarkSword stated, using the piano roll adds a lot more complexity to your groove. Quantizing your notes gives it a more "natural" feel compared to your typical sixteenth note groove. Changing the note velocity, placement of notes and all that other goodness drives your percussion groove in a more naturalistic approach compared to being directly on the beat. Try that out and mess around with the piano roll and quantizing and changing the note velocities for each note and you'll find that you can create some pretty neat grooves. Enjoy

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Practice doesn't make perfect. Perfect practice makes perfect.

Fruity Loops was the first music software i ever learned how to use, and Im pretty sure theres no way to change it back, mate

Although I rarely just use the sequencer, and end up putting everything in piano roll.

Im guessing if they implemented an option to change back to sequencer and you had a piano roll section with dozens and dozens of notes on,
it would create havoc on the sequencer when changed back- maybe thats why you cant do it.

~SiK