ARTCC Controller reported observing on radar a NMAC between two departures from RDM Airport. RDM Tower issued control instructions to separate the traffic.

Narrative

Aircraft X departed RDM runway heading off of Runway 5; assigned 140 for altitude. Tower had Aircraft Y depart east bound. I was not talking to either aircraft until the conflict was resolved; but they nearly merged at the same altitude (around 5;400 ft; below my MIA). It appeared Aircraft X and Aircraft Y got each other in sight at Aircraft Y turned slightly northeast to parallel Aircraft X; but they got to within maybe .1 miles at the same altitude. The pilot didn't say NMAC but it was definitely a NMAC. It appeared that Aircraft X stopped climbing to avoid Aircraft Y for a moment. It is so smoky in the area with all of the wildfires; it is very difficult to get traffic in sight. I tried issuing a southbound vector in the blind to the Aircraft X and tried calling traffic in the blind; but they were still on Tower frequency. Tower told my d side training team that they issued instructions to the aircraft to resolve the situation; but it was definitely one of; if not the closest calls I've had. The fact that Redmond Tower has passenger jets and other aircraft and all the other nearby airports with no radar in the Tower renders them incapable to safely navigate aircraft in and out of the area; and it is only a matter of time before there is a midair collision that could be prevented. This sector is designed to fail. As long as it is not a class C and Tower does not have a radar; we are going to watch a lot of people die one day; and I hope I am not working when it happens. It is unsafe and no one at ZSE is suited to work the airspace.