22K per night at the ANA is a pretty good rate, I'd say.

Need some help again locating a decent area to stay in, preferable close to a station that can take me to Roppongi and Shibuya quite easily (a line going to Shinjuku would be an added bonus).

I see that the Aoyama-Itchome station fits the bill perfectly (1 stop to Roppongi, 2 to Shibuya and 3 to Shinjuku). What is the place like though, is it sort of like "the middle of nowhere," with the only option to bail out of the place by train each time? Or will there be stuff going on as well there?

Other option I'm looking at is the Tameikesanno/Kokkaigijidomae station area (connections to all three places, but Roppongi-Itchome instead of the main station, and Shinjuku-Sanchome instead of the main one there as well - though in this case the Sanchome one seems to be better placed). Is this the type of place where you only head back to crash for the night or will there be anything happening in the evenings? The added bonus of this place is that it's connected to the red line, so once I take the Nex into Tokyo station I can just hop onto this line and not have to switch trains.

You can find things to do in the evenings in all those areas but they are mainly commercial areas so they are quieter, especially on the weekend. I'd be thinking about staying around shinbashi/shiodome, hundreds of izakaya to eat/drink and the oedo line will take you through roppongi to shinjuku with one change to get to shibuya. Would only be 2000 yen or so to catch a taxi back from roppongi once the trains stop.

I'd suggest staying near Shibuya station. You can get there from NRT with a limo bus or N'EX. It's three stops from Shinjuku on the Yamanote line. And it's a short bus ride to Roppongi. Buses to Roppongi leave from the stop marked 51 on this map. Look at the destination signs on the front and side of the bus. It will say "Roppongi" in English:
http://www.kotsu.metro.tokyo.jp/bus/noriba/shibuya.html

I suggest you check hotel sites (Tripadvisor / hipmunk etc.) to find reviews and prices to help you choose the hotel.

Why Roppongi, of all the neighborhoods in Tokyo?

For the nightlife or the shopping, I guess.

I thought Ginza was for the shopping. Rappungi is for the nightlife.

Hmm, I thought Shinjuku was for the shopping, no? Or Shibuya? :) Then again I live in Singapore so I'm fed up with shopping, malls, etc... ;) The only thing I think will get me interested are any electronics goods/gadgets that are unique to Japan.

Roppongi for going out in the evenings, that's the plan.

The problem I'm having is that I need a single/double room for myself and a twin room for some friends that are flying in later that day. As soon as the prices start edging towards the ANA IC level we keep reverting back to it, but I know right now that we won't have the time to relax and use the facilities like the pool, so I'm still looking at other options. I checked out other hotels in Roppongi and Shibuya but no success.

Finding a room for myself would have been done a long time ago, but it's the twin room that's causing problems (most seem taken compared to double rooms). How is the Shiba Park Hotel? They have a twin and a double so that is good, and they are right next to a subway line that goes to Roppongi (downside is the airport transfer - being 3 stops from Tokyo station... but having to switch lines at every step of the way)

Is the Shiba Park Hotel in an interesting area though, or is it a place with nothing going on so we'd basically be going from the hotel to the trains all the time?

Shiba Park hotel is about 3 minutes walk from the izakaya area near daimon and about 10 minutes walk from shinbashi. Basically the area is about the equivalent of the area around the ANA, a mainly commercial area with some places nearby and some areas with heaps to do within about 10 minutes walk.

The couple of comments I'll make is to stop obsessing about the subway so much, when you've got 3 or 4 people as you seem to a taxi between all these areas will cost about the same as the subway and if you are out at night the trains would have finished long before you're heading home. Also I've stayed at the ANA many many times and the only 'facilities' I've ever used is Mixx bar and I've never felt that this was somehow a waste.