The kernels provided in ROSA Fresh R5 already include drivers for many WiFi adapters with Realtek's chips.

If the drivers are not provided for some models (e.g., RTL8723BE and RTL8812AU in kernel 3.14.x) or are not working good enough, you may try the following.

Note that dkms-rtl8812au may not work on the kernel 4.0 or newer yet.