Dalton for Rofi is a Rofi port of Dalton Theme, check out Dalton Website to get more dalton theme ports.
Dalton is a minimal theme for Rofi, very black with some blue.
First, you need to install the Fira Code Font, if you is in a linux distro, you can download Fira Code using your package manager, see the instructions in the Fira Code install guide
Create the directory .config/rofi, and copy the dalton.rasi to this folder.
Now, you can use the argument -theme with dalton, like this:
rofi -show drun -theme dalton