The Rocket Boots are a unique piece of equipment in that they do not offer any stat bonuses, but instead have the effect of increasing your character's movement speed. The Rocket Boots are the only pair of shoes that Arma can wear and they are completely exclusive to her. When equipped, they increase her regular walking speed substantially.
The following table lists the times with and without Rocket Boots. The test was conducted on Amber Garden 30th Floor (Tielle Boss Fight Room). The time is how long it takes to move from the very bottom to the top of the stage. [Note: Fusion Bonuses do not effect the movement speed, see the table for Jet Boots]
Since Arma can't dash like other characters, the Rocket Boots increase Arma's ability to maneuver considerably at the cost of an equipment slot. Since Arma can equip heavy armor and helmets and can fight at long range, she can get away with sacrificing defense a bit more than Charme and Griff could with the Jet Boots.