Hi,
You should install MLNX_OFED latest driver- version 3.3-1.0.4.0 that supports both Ubuntu 15.04 and 14.04 versions.
There should not be any problem to work with this type of card in Ubuntu 15.04 and 14.04.
Also ConnectX3 Pro card does support SR-IOV and ROCEv2.
MLNX_OFED driver can be found in the following web page:
http://www.mellanox.com/page/products_dyn?product_family=26&mtag=linux_sw_drivers
Regards,
Viki