Buspar 10 mg, Effexor XR 225 and Remeron 15 mg. Are these OK to take together?

There are 3 Major interactions between your medications. If these were prescribed by the same Dr., he/she is most likely to be aware of these potential interactions and your Dr. has outweighed that the benefit of taking these medications is greater than the potential risk.
If they were prescribed by different Drs. and they are not aware of what you are taking, I suggest you do not take them until you can reach them and inform them of the potential interactions.

Interaction report:
https://www.drugs.com/interactions-check.php?drug_list=441-206,2296-1523,1640-1015

If you feel uneasy with the potential interactions, I recommend you contact your Dr. and further discuss them.