No air flow in room
 

I have a room that has a 90 from a main duct. There are two rooms, the last room has a 90 bend and gets circulation of air fine, but the room before doesn't get circulation because the vent duct just comes off the main duct with no bend or direction. What can I do to fix this? I live in Florida and that has caused the room to typically be 10-15 degrees hotter than the rest of the house. It is a rental home and the landlord has dated that it has never been a problem for previous renters and he isn't goin to invest in any costly solutions

Easier said then done, but could you either take some pictures and/or describe this a little better? I dont' quite understand?
Your saying the last room has a "90 bend"; are you saying it 90's off from the top of the supply vent and then into the main trunk line?
Assuming you have maybe a 6" round pipe or flexible duct?

Cover the heat duct(s) for the warmer room(s) partially.

If the room does not have a return duct then leave the door to the hall open.

Can you remove the duct louvers and look inside the duct for obstructions? Do you have furniture or other items blocking the air flow in the cooler room(s)?

Nothing beats return air intakes, since there rarely can be too many.

I have had several multi-level (3 or 4 levels) homes and put in 2 returns in every room (one high and one low in the same stud cavity with the ability to shut off either one). This was because of the highly variable seasonal climate (-20F to 100F). The exception was the conditioned basement/lower level where the returns were always close to the floor level.

Dick