Where to place tempdb and logfiles
RAID 1 is less suitable for any of Data file, log file and tempdb file. Although RAID 1 provides redundancy by mirroring and also provides bit of a fault tolerance it is kind of outdated with arrival of RAID 5 and RAID10(or RAID1+0). Best is to keep data, log and tempdb on differnt physical drives which are configured either in RAID 5 or RAID10. RAID 10 is more preffered but is costly as compared to other RAID technologies.

If you have restriction with RAID 1 you can use it but then make sure you separate data,log and tempdb files on different physical drive to avoid I/O contention.

Above suggesstion were given because you asked about seggregating files. In many environment because I/O load is relatively less data and log files are kept on same drive, even tempdb is placed on same drive where other files are present. According to surrounding/env/load  we can seggregate files to get optimum performance.