root@debian:/opt/iiab/iiab/scripts# ansible --version
ansible 2.4.0.0
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/root/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/dist-packages/ansible
  executable location = /usr/bin/ansible
  python version = 2.7.13 (default, Jan 19 2017, 14:48:08) [GCC 6.3.0 20170118]

Add a "contrib" component to your existing repository line in /etc/apt/sources.list; for example:
# Debian 9 "stretch"
deb http://deb.debian.org/debian/ stretch main contrib non-free

root@box:~# apt install firmware-brcm80211/stable

root@box:~# ifconfig
wlp4s0b1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 169.254.44.103  netmask 255.255.0.0  broadcast 169.254.255.255
        ether 2c:b0:5d:cf:46:fa  txqueuelen 1000  (Ethernet)
        RX packets 215  bytes 42915 (41.9 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 237  bytes 70895 (69.2 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

root@box:~# lspci
02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 06)
03:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 06)
04:00.0 Network controller: Broadcom Limited BCM43224 802.11a/b/g/n (rev 01)