BOSS and ROLAND are essentially the same company and use the same TRS midi standard (type A).

TRS cables are exactly the same as stereo audio cables, so you might already have these lying around. The only difference is that the RC-5 pedal has a 1/4" jack and the SP has an 1/8" jack, so you might just need to pick up an adapter.

1/4" to 1/8" cable

OR

1/4" to 1/8" adapters depending on what sized TRS cables you might already have

Edit: not endorsing these brands specifically, just wanted to provide a visual