The planting of clematis with roses works extremely well, they can add a different colour, size and shape of bloom and also extend the flowering season.
If you wish to add extra colour in the spring, take a look at the atragene group, these have their main flowering period from mid to late spring and leave very nice seedheads for later interest. All are suitable to grow with roses. Avoid planting the very vigorous spring flowering montanas with roses - the only exceptions being montana 'Freda' who is much more ladylike in her growth and habit as is montana 'van Gogh'.
Many clematis have two flowering periods, usually late spring to early summer, then late summer to early / mid autumn. Any of these would be suitable to grow with roses. You will find these in the catalogue if you look for flowering months indicated as May-June & September, or see the Early Large Flowered group online here.
Clematis that bloom later in the year i.e. mid summer to autumn are useful to grow with roses as this can extend the flowering period to later in the year. You will find many clematis whose flowering period begins in June or July and goes on until September or October. Good examples can be found in the Late Large Flowered Group and Viticella Group.
Beware of planting tangutica 'Lambton Park', 'Bill MacKenzie', rehderiana and terniflora with roses unless the rose is very vigorous and already well-established.
Try under-planting with any of the non-clinging (non-climbing) types of clematis. 'Alionushka' is lovely with white or cream roses such as 'Swany', or perhaps try x durandii with roses in shades of yellow.
Please refer to the Diversifolia group for further suggestions.
White Roses - almost any colour and shade of clematis would be suitable. If you want a combination of pastel colours try a pale blue clematis such as Blue Angel, 'Prince Charles' or 'Perle d'Azur', or a pink clematis, maybe 'Hagley Hybrid', 'Comtesse de Bouchaud' or 'Pink Fantasy'. For a more striking contrast try a red clematis perhaps 'Rouge Cardinal', 'Rüütel' or 'Westerplatte'.
Pink Roses - unless you are very brave simply avoid pink clematis - try any of the blues such as 'Elsa Späth', 'General Sikorski' or 'The First Lady', or a purple, perhaps 'Jackmanii', 'Romantica' or 'The President'.
Peach / Apricot / Cream Roses - any of the blue, purple or red clematis would make excellent companions. For example, the apricot-yellow rose 'Lady Hillingdon' looks superb with the red 'Södertälje'.
Red, Deep Pink and Purple Roses - try pale / light blue, mauve or white clematis. A favourite combination in our garden is the dark red rose 'Etoile de Hollande' with the white clematis 'Snow Queen'.
If we can be of further help on this topic please call the nursery on 01953 850407.
For detailed rose advice please contact our friends at Peter Beales Roses - https://www.classicroses.co.uk . or call them on 01953 454707