Actually, they do. Both Miller and Aldridge command double-teams when made the focus, as both proved when Roy was injured. They're just not as good as Roy.
They do not play the same position and can really sub for him, which is the point I am making.
But, in any case, I disagree with you. Even though the team does have other players who can command a double-team, it would still be silly to limit Roy's minutes after 4-5 bad quarters.
I think we have seen this pattern going forever in NBA teams, coaches letting their stars work themselves out of slumps. Of course, if they can not do so, they are no longer stars and we get the answer to the question of - what separates stars from role-players...
That's a little too simplistic, IMO. Where is the cut-off for when a player drops from "star" to "role-player?" There is no cut-off, it's an unbroken continuum from greatness (with LeBron James defining one end of the continuum currently) to barely-in-the-NBA (Tolliver, perhaps, being a good example of that end). There's no specific point where a player becomes "not worthy of consistent minutes, has to justify his presence on a minute-by-minute basis." The principle the vast majority of coaches use is to play their best players the most minutes. By pretty much any accounting, Batum is one of the team's five best players at least. He should certainly be getting a larger minute allotment in accordance with that.
Someone becomes a role player when he can no longer be counted to carry the team and be one of it's best players consistently. I honestly think that "play your best players" long minutes is right when there are no alternatives and the outcome of the games is not that important, if a team is bad and is developing it's young players - you play them more during bad periods, when it's trying to win to contend, as the Blazers are right now, this is less important.
The fact of the matter is that when Nic plays bad, Nate brings Wes in and if he plays better - will keep him long minutes, if Wes does not play well - he will try something else.
Let's look at these last 2 games, Nic had a negative game-score in both of them (bad), his offense was not there, his defense was not there. In the first, he brought Wes in, Wes did not play well (Game score 0.2) - and Wes, just like Nic, got only 17 minutes, last game, Wes had a good game, game score of 10 or so - and he got heavy minutes. Nate was coaching to win - and that's what I would like him to do with a team that can contend. This is not an expansion team, this is not a develop your players above all - Nic is a role player at this stage of his career on a team that wants to contend. Nate plays him the right way.
BTW - if you look at Wes's game log you will see that the pattern works the same for him - he had a good 1st, 3rd, 5th games, big minutes, bad 2nd, 4th - short minutes.