Conditions caused by complete deafness
To support players with complete deafness, it is important to allow other communication methods greater accessibility. If the player relies on visual communication, for instance, there are several environmental options that can be manipulated. This guidance is specifically suggested for individuals that are not able to utilize an aide to fully or partially restore hearing ability.
Ensure that enough lighting is on so that other players are the table are visible, including areas such as the tabletop, hand, and faces of other players. Dimming lights are fine for setting a mood, but the ability to see gestures or lip movement from across a table may be of greater necessity. Communicating with the player in advance should allow you to create the ideal environment.
If it is possible, position player seating so that a deaf player has visibility of all other players. Having players seated in a circle around the table, rather than in a line means that a player is not obstructed by another player in between.
Additionally, whenever it is a possibility to provide resources necessary for communication as well as safe spaces to work with those disabilities. It is possible that the player may have an interpreter or assistive device for communication. Provide resources and space for the interpreter, and any connectivity or access to power/internet for a device.
Communicate regularly with the player. There is the potential that a fear of an inability to deliver information verbally to a deaf player may make a player or GM unconsciously reduce the amount of dialogue they might normally have with the player. Be aware of this potential, so that you are not leaving a player out.
You can use visual indicators to keep track of and alert players of turn order. Once turn order is set, you can for instance position named cards in the order that turns take place, Shifting the card forward for the character whose turn it is. Likewise, if environmental or event descriptions are scripted in your roleplaying sessions, you can create cards with this information and provide it to the player as those environments/events come up.
Likewise, if you have access to a mobile device such as a laptop, you could possibly free Speech to text applications which can potentially show (with as close a fidelity as these applications can) somewhat of a live closed captioning. Here is an example of how to do so.
- Sign up with or log into Google, and gain access to Google Docs through Google Drive.
- Create a document, label it, and share that document with the player.
- As you play the game, you can select the Voice Typing option under Tools.
- If the player has their own device, they can see the text appearing as you voice type it.
- If the player does not have a device, set font to large and turn your device to face the player.
- You can find out more information about Google's Voice Typing here 
It is never a bad idea to take the time to learn sign language. There are many resources available for free online that have videos and guided lessons.