Hello!
I agree with AHBD; beardies wont starve themselves. The lack of enthusiasm for roaches may have nothing to do with the impaction, but could be a normal change of appetite. My boy Dezi loves one food for a while, and randomly decides he does not want that, and loves something else! It often happens at an inconvenient time, like right after I purchase a few hundred crickets, he decides that his new fave is superworms. So, in time, your beardie could go back to his dubia loving. Just offer one every few days, and see what happens.
Meanwhile, I have some experience with keeping large cricket colonys, and perhaps I can help there...a healthy batch of crickets should not smell bad. I keep mine in large buckets with good ventilation--holes in lid covered by wire mesh. The vents are so important because the crickets produce a lot of humidity, which leads to fungus/bacteria, etc. Any deads must be removed immediately, or a mass die off begins from the gases produced by the bodies. That causes a foul odor. I remove all deadies along with any molt, body parts or refuse, every day.
The water is also crucial...I have a shallow lid with a paper towel crumpled in it, for their water. They die fast without it, but are so stupid they drown easily, so that is why the paper towel is needed. Too much water causes too high humidity...if any moisture collects on sides or lid of bucket, you will need better ventilation holes in lid. The water and towel are also changed every day. Feed dry cricket food, monkey biscuit or dry beardie food, and a few carrots. Many other foods rot quickly and cause die off. Avoid feeding other fruits and veggies, which are prone to causing fungus and mold. Dry off carrots before placing in bucket. Keep buckets where temps are steady--70-74* is a good range. Do not over fill buckets. They will start to cannibalize if over crowded.
I like some pieces of egg carton in bucket, to give the crickets more vertical space. If cut a size that fits in a jar, it is easy to simply pick up a piece of egg carton and shake it inside the jar, at feeding time. That makes catching them fast and easy. (Then I can add some calcium/vit.D powder to jar and shake gently to coat crickets before feeding to my dragons) A good substrate is the wood shavings found in pet stores--not cedar! , but the light colored fine shaved ones, I think they are pine. If I see any sign of discoloration, change in smell, whatever, I quickly transfer all crickets into a fresh bucket with all new substrate and egg carton before a die off begins. The crickets can die off over night, once that starts. I keep a spare clean bucket ready with substrate and egg crate, for just that purpose.
So, that should help some, until your picky beardie decides to return to eating dubias. I have never kept dubias, so I do not know how labor intensive they are, but crickets are almost as much work to keep as the beardies! I lose only a few cricks, maybe three a day per bucket. If you have more deadies than that, you may need to adjust something.
Good luck!