Rofi, like dmenu, will provide the user with a textual list of options where one or more can be selected. This can either be, running an application, selecting a window or options provided by an external script.

On Gentoo just use the command below with root or add the sudo in the normal user

emerge rofi

To test to see if it is working normally, run the command:

rofi -show run

To create a shortcut for the super + d key combination to open Rofi, simply edit the vim .config/sxhkd/sxhkdrc configuration file and insert the following line:

super + d
	rofi -show run

For you to customize rofi theme, run the commands below in order

mkdir ~/.config/rofi
rofi -dump-config > ~/.config/rofi/config.rasi
wget https://raw.githubusercontent.com/ricwtk/rofi-themes/master/input-emph-topbar.rasi -O 
~/.config/rofi/input-emph-topbar.rasi
sed -i '/configuration {/a theme:  "input-emph-topbar";' ~/.config/rofi/config.rasi

Okay, now whenever you type super + d open Rofi.

rofi gentoo bspwm