Hi,
JEE Main has two papers:
Paper 1: for all undergraduate engineering programs and
Paper 2: for Architecture and Planning programs.
If you are desirous of pursuing B. Arch. in IIT Kharagpur or IIT Roorkee, you must clear the Architecture Aptitude Test (AAT). The contenders who have secured a rank in JEE (Advanced) are eligible to sit for AAT. The test will be be held only at the seven zonal IITs. This means, in order to get a B. Arch course in these two institutions, one has to clear Paper 1(B. Arch. / B. Planning.) of JEE Main, JEE Advanced and AAT. For admissions to institutions other than the IITs, JEE Main Paper 2(B. Arch. / B. Planning) scores are taken into account.

Hope this helps.
Good luck.