Can I use an SSD for main drive and a RAID configuration afterwards?

Yes, but method depends on your system (your configuration does not state which MB.

Method depends on available sata ports.
If you have only intel sata ports you would probably need to reinstall operating system and programs on SSD - Reason is changing from AHCI (i'm quessing that is what you had the BIOS set to).
Basically you would (After Backing up all of your Data):
(1) Change BIOS to Raid. Disconnect HDDs and Just SSD installed.
(2) Install windows, when complete
(3) reconnect HDD enter raid setup and set up raid0 for the Two HDDs.
(4) from windows disk management, initialize/partition and format HDDs.

If you have two controllers and 2nd controller supports raid then move the HDDs to the 2nd controller (ie a marvel controller), set up raid - Done.

KNOW for the $64,000 question, why do you want to use raid 0??

Raid0:
Only improves sequencial read / writes, does nothing for access time nor does it improve the 4ki small file random read /writes. Sequencial performance is only important if you do a lot of large file work, ie editting/encoding large 1 gig video files, work a lot on large jpeg photos, large spreedsheets, or CAD/CAM drawing files. May improve loading game map files (but not a big performance boost here).