You could do this.

1. Spring bulb means that they will flower in early or mid spring.  First you should check the bulbs hardiness to make sure that they can withstand your zone 4 temperature of -30 to -20 degrees Fahrenheit during the winter.  If yes, you should plan them around October before the first frost since these bulbs require a chilling period to break the dormancy of the embryonic plant inside the bulb.  

2. I would use the planter for planting annuals since your zone is too cold for perennials.

3. Most likely, the bug on your roses is called 'Japanese Beetle'.  I use the following.  Good luck

https://www.lowes.com/pd/BAYER-ADVANCED-Rose-and-Flower-Insect-Killer-24-fl-oz-Insect-Killer/1000180245