If no one is occupying the unit and you are in the cold winter months... unplug all appliances including the fridge (they love nesting near the warm compressor motor, and the dishwasher also provides a warm humid environment), open all cabinets and appliance doors. Then open the windows and patio door for a day or two.
Roaches and their eggs die if exposed to temperatures under 40 Deg F for 10 hours. Freeze them to death.
Then, look behind all cabinets, appliances, heating convectors and seal up any holes and voids. Use "Great Stuff expanding foam, plastic sheet and tape, whatever does the trick.
Then use Gentrol capsules to stunt their growth so they do not reach egg-laying maturity. Gentrol is good fo 2 to 3 months.
Get a duster and some Cimexa dust. blow a light film into cracks, under cabinets, stove, bathroom cabinets, etc. Cimex is harmless micro silica that sucks up moisture (it is used to keep electronics and beef jerky from getting damp and moldy). Roaches walk across it and ingest it when they clean their legs. It dehydrates them and kills them.
Apply roach baits. Most exterminators just put baits on cabinet edges. Rutgers university did a study and found baits are most effective in tight spaces as roaches feel safer when eating if they have at least TWO sides of their body making contact with a surface. They recommended making "roach tacos" - basically take a 4 inch square of wax paper. Fold it in half to form a triangle. Aplay a pea sized gob of roach bait at the center, and leave them around where roaches hang. They found a significant reduction in surveyed roach population when applying bait this way.
As for the dishwasher, I too had a tenant in Alexandria who NEVER cleaned the kitchen and NEVER notified me of the roach problem! The roaches bunched up in the control module and shorted it out. It was an older dishwasher, but still worked fine until the roaches. The control module was sealed in a way I could not open it to get the dead roaches out and repair the circuit.
Repair person came and tried to sell me a new dishwasher to include a $50 a month maintenance program to cover any repair. Hmm $50 a month x 12 months = $600 plus the $350 for new dishwasher! I paid him the $100 service visit and told him to get lost.
Got a new dishwasher at Home Depot and found a huge hole in the wall behind the old dishwasher that building maintenance had cut to access pipes in the wall! I sealed that up with plastic and tape! Roaches had been coming in from other units via that hole!