All of the time!

I do a lot of sound design work. When possible, I've done implementation of the game audio - be it within a middleware program like Fmod or something else like XML, actionscript or a json file. I also help direct and produce voice over actors. At times, I do the voice over work myself as well. I also have to read, sometimes write and always negotiate the contracts. I'm also heavily involved with maintaining my website as well as all other PR materials I use for branding. For smaller projects, I've also helped with game design, level design, etc. And almost always, I help out with some element(s) of QA because I enjoy testing the game.

Happy to help!

So how would that work usually, would you be hired mainly as a composer, and then the other tasks would just get "pushed" over to you, or would the developer/you clearly state all the different tasks you'd be performing from the start?

The later, as much as possible. I try to get set my tasks in a defined and clear manner. In some cases, I've opted to take on additional tasks at an additional cost.

Would you say that basic coding and middleware skills are beneficial in order to get hired for a project?

You certainly don't have to be a programmer. I'm not! But the more you know about other areas of game development, the easier you can discuss ideas and approaches with various parts of the team. That's always a benefit. I understand enough to be able to chat with artists and programmers and see how my approaches can align with theirs.

As a contractor I have been hired many times in separate roles and combined roles. However, it's pretty clear up front when drafting the contract what my role will be and what the rates are for each individual component. Make sure you always have a signed contract - agreement between both parties on what is expected and how long it will take and how much you will be compensated.

When you have more skillsets than a single one, you will not only understand more of game development but at the same time broaden your employability even if you don't use the knowledge immediately.

Sometimes a client will also hire me as a sound designer when they only were looking for a composer, but again, I informed them and it was agreed before hand and not added as an afterfact.

However, that being said, in-house work is a little more flexible. I've been hired by multiple companies as sound designer only and even the role states "there is no music composition involved" every single one of them I have written music for after a while to some degree - even if it is for internal use only. Usually in-house work does not have enough work to keep a composer fully utilized so having other skills in this regard will help greatly. Not everyone is equally as passionate about sound design as they are composing.

It's much easier to find work if you can fill multiple roles on the development team. I almost always do sound design work in addition to music composition. I would say the big overlapping categories that you should be able to fill are Effects, Voice-Over, and Implementation.

For effects you should be able to do more than just pound away on a midi keyboard or pull something from a library. I find myself doing a lot of custom foley work for games. You should be very familiar with all of your editing tools as you'll be using them just as frequently as you do in music mixing/mastering.

Voice Over work would include Casting, Directing, and Acting (if possible). Get to know people who are good non-union talent. For every 1 actual actor, you're going to find 100 people who are in the 'someone told me I have a cool voice' category. So get to know your local talent agents and get to know the good talent from the bad. You should also be able to cast for roles and be able to direct the performance. Once again non-=union talent is very hit or miss and they can often be very hard to direct. If you have some acting talent it can always help to offer your services as well. At the very least you should be able to do reaction lines and simple 1 word responses.

You should also be able to implement the audio in addition to creating it. Learn the common tools like Wwise and Fmod. Practice implementing audio in engines like Unity and Unreal.

Absolutely, writing music is the easy part. I made a point of learning 3ds Max, as well as python, javascript and c#. I have organised productions and been involved in writing pitch documents, story boarding and scripts; very much a part of the team.

It is vital to know more than the basic skillset required for each job; you have to be able to see beyond, the bow of your own ship.