I can see what @MrsDThomas is saying, @LogBasketOfDreams - though I think there is a middle ground. You can decide which toys or games can be brought through into the sitting room, and which have to stay in the playroom. For example - anything with lots of bits, like lego, or meccano or jigsaws, and anything messy like colouring or painting, stays in the playroom, but things with fewer bits can come into the sitting room - but only one at a time - one board game, for example, so if they want to stop playing with the thing they've brought through, they have to take it back before they bring the next thing.
That way, they can balance time in the playroom and time with you, and you don't end up with lots of toys in the sitting room, so clearing up is easier.
When my dses were small, we didn't have toys in the front room, as a general rule. Things came through sometimes, but were taken away when finished with - and as most of the toys lived in the dining room, or in the playroom (when we moved to a house that had a room that could be used as such), and as they had a tv with a video player in there, they were happy to play in there most of the time.
To be honest, though, I can't actually remember how we achieved this - the boys are 23, 25 and 27 now, and the early years are lost in the mists of time! Looking back, I think it helped that, when they were little, we lived in a house with a front room and then a dining room leading onto the kitchen, and I used to keep the front room shut up, for most of the day - we did all our living in the dining room, where all their toys lived, and where I could keep an eye on them from the kitchen when I was doing things out there. It had (just) enough space for a table and chairs, plus a cane sofa and chair, and their toys, and their small table and chairs, so it was a comfortable place for us all.
It didn't have a TV, though - that was in the front room, and I used to go in there for my lunch, and watch tv whilst they had their afternoon nap, then, when they came down, they could watch the children's programmes or a video.
When they were older, they definitely liked having their own space - by that time we could afford sky multiroom, so they had their own tv in there, and could watch the things they liked - mainly football - and play playstation, whilst I got the use of the front room TV!